Financial Instrument [Axis] Certificates of Deposit [Member] Municipal Bonds [Member] Award Type [Axis] Stock Option Plans [Member] Plan Name [Axis] 2007 Plan [Member] Loss Contingency Nature [Axis] Standby Letters of Credit [Member] 2017 Plan [Member] Award Type [Axis] Non employee directors [Member] Range [Axis] Maximum [Member] Individual Employee [Member] Employee Stock Ownership Plan (ESOP) Name [Axis] Employee Stock Ownership Plan [Member] Adjustments for New Accounting Pronouncements [Axis] ASC 606 [Member] Scenario [Axis] Units Delivered [Member] Milestones Achieved [Member] Finite-Lived Intangible Assets by Major Class [Axis] Backlog [Member] Equity Components [Axis] Common Stock [Member] Capital in Excess of Par Value [Member] Accumulated Other Comprehensive Income (Loss) [Member] Retained Earnings [Member] Treasury Stock [Member] Unearned ESOP Shares [Member] Document And Entity Information [Abstract] Entity Registrant Name Entity Central Index Key Document Type Document Period End Date Amendment Flag Current Fiscal Year End Date Entity Filer Category Entity Small Business Entity Emerging Growth Company Document Fiscal Period Focus Document Fiscal Year Focus Entity Common Stock, Shares Outstanding Entity Current Reporting Status Entity Interactive Data Current Entity File Number Entity Incorportion, State or Country Code Entity Shell Company Statement of Financial Position [Abstract] ASSETS: Cash and cash equivalents Investment securities Trade accounts receivable, net of allowance of $3,000 Income tax receivable Inventories: Raw materials Work-in-process Costs related to contracts in process Total inventories Prepaid expenses and other current assets Total current assets Property, plant and equipment, net Total assets LIABILITIES AND STOCKHOLDERS' EQUITY: Accounts payable Accrued expenses: Salaries and wages Vacation Dividends Other Payroll and other taxes withheld Contract liabilities Income taxes payable Total current liabilities Deferred tax liabilities Total liabilities Commitments and contingencies (see Note 5) Common stock, par value $.33-1/3 per share Authorized 10,000,000 shares; Issued 3,029,874 shares as of September 30, 2020 and June 30, 2020. Outstanding 2,402,633 as of September 30, 2020 and June 30, 2020 Capital in excess of par value Accumulated other comprehensive loss Retained earnings Total stockholders equity before ESOP Less: Cost of 627,241 shares of common stock in treasury as of September 30, 2020 and June 30, 2020 Total stockholders' equity Total liabilities and stockholders' equity Trade accounts receivable, allowance Advance payments of costs related to contracts in process Common stock, par value Common stock, shares authorized Common stock, shares issued Common stock, shares outstanding Unearned ESOP, shares Treasury stock, shares Income Statement [Abstract] Net sales Cost of sales Gross profit Selling, general and administrative expenses Operating income Other income: Interest income Other Total other income Income before provision for income taxes Provision for income taxes Net income Other comprehensive (loss) income, net of tax: Unrealized (loss) gain on investment securities Total comprehensive income Net income per share: Basic Diluted Weighted average number of shares outstanding: Basic Diluted Dividends per share: Statement [Table] Statement [Line Items] Balance, beginning Balance, beginning, shares Net income Other comprehensive income (loss), net of tax Total comprehensive income Stock options exercised Stock options exercised, shares Stock-based compensation Dividends declared on common stock Purchase of treasury stock Purchase of treasury stock, shares Balance, ending Balance, ending, common shares Statement of Stockholders' Equity [Abstract] Other comprehensive income, tax portion Dividends paid per share Statement of Cash Flows [Abstract] Cash Flows from Operating Activities: Adjustments to reconcile net income to net cash provided by operating activities: Depreciation ESOP compensation expense Deferred income tax benefit Changes in assets and liabilities: Decrease in trade accounts receivable, net Increase in income tax receivable Increase in inventories, net (Increase) decrease in prepaid expenses and other current assets Decrease in accounts payable Increase in accrued salaries and wages Decrease in vacation accrual Decrease in ESOP payable Decrease in other accrued expenses Increase (decrease) in payroll and other taxes withheld Increase in contract liabilities Decrease in income taxes payable Net cash provided by operating activities Cash Flows from Investing Activities: Additions to property, plant and equipment Purchase of investment securities Proceeds from sale/maturity of investment securities Net cash provided by investing activities Cash Flows from Financing Activities: Dividends on common stock Purchase of treasury stock Proceeds from exercise of stock options Net cash used in financing activities Increase in cash and cash equivalents Cash and cash equivalents, beginning of period Cash and cash equivalents, end of period Supplemental Schedule of Cash Flow Information: Income taxes paid Supplemental Schedule of Non-cash Financing Activities Accrual of dividends Basis of Presentation [Abstract] Basis of Presentation Investments, Debt and Equity Securities [Abstract] Investment Securities Net Income per Share [Abstract] Net Income per Share Share-based Payment Arrangement [Abstract] Stock Based Compensation Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Revenue from Contract with Customer [Abstract] Revenue Recently Issued Accounting Standards [Abstract] Recently Issued Accounting Standards Employee Stock Ownership Plan [Abstract] Employee Stock Ownership Plan Schedule of Available-for-Sale Securities Schedule of Contractual Maturities Schedule of Fair Value Assumptions Schedule of Stock Option Activity Schedule of Changes in Non-Vested Stock Options Schedule of ESOP shares Schedule of Available-for-sale Securities [Table] Debt Securities, Available-for-sale [Line Items] Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Fair Value Contractual maturities of available-for-sale securities Less than One Year One to Five Years Fair Value Anti-dilutive securities Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Title of Individual [Axis] Statistical Measurement [Axis] Stock based compensation expense Deferred tax benefit related to stock based compensation Unrecognized compensation costs Period in which compensation cost will be recognized Deferred tax benefit related to unrecognized compensation costs Vesting period Expiration period Authorized shares under plan Granted Outstanding Cash divided paid Special cash divided paid Percentage of total number of shares subject to options or awards, single fiscal year Number of shares subject to option or award, single fiscal year Total intrinsic values of the options exercised Vested and exercisable shares TotalStockholdersEquityBeforyEsopAndTreasuryStock Number of Shares Subject To Options Balance at July 1, 2020 Exercised Forfeited or expired Outstanding at September 30, 2020 Vested or expected to vest at September 30, 2020 Exercisable at September 30, 2020 Weighted Average Exercise Price Balance at July 1, 2020 Granted Exercised Forfeited or expired Outstanding at September 30, 2020 Vested or expected to vest at September 30, 2020 Exercisable at September 30, 2020 Weighted Average Remaining Contractual Term Outstanding Granted Vested or expected to vest at September 30, 2020 Exercisable at September 30, 2020 Aggregate Intrinsic Value Outstanding at September 30, 2020 Vested or expected to vest at September 30, 2020 Exercisable at September 30, 2020 Number of Shares Subject to Option Non-vested at July 1, 2020 Granted Vested Forfeited or expired Non-vested at September 30, 2020 Weighted Average Grant Date Fair Value (per Option) Non-vested at July 1, 2020 Granted Vested Forfeited or expired Non-vested at September 30, 2020 Contingent liabilities Prospective Adoption of New Accounting Pronouncements [Table] Item Effected [Line Items] Accounting Standards Update [Axis] Contract liabilities Revenue Intangible assets Percentage of estimated shipments Schedule of Employee Stock Ownership Plan (ESOP) Disclosures [Table] Employee Stock Ownership Plan (ESOP) Disclosures [Line Items] Number of hours worked per year to quality for the plan Shares repurchased Value of shares repurchased Allocated shares Committed-to-be-released shares Unreleased shares Total shares held by the ESOP Fair value of unreleased shares ASC 606 [Member] Represents the amount of dividends accrued in noncash investing or financing activities. Amount of deferred tax benefit attributable to unrecognized share-based compensation. Minimum number of hours worked per year for nonunion employees to participate in ESOP. Information by name of employee stock ownership plan. The entire disclosure for employee stock ownership plan. Units Delivered [Member] Individual Employee [Member] Units Delivered [Member] Non employee directors [Member] The number of shares subject to option or award in a single fiscal year as outlined in the plan contract. Percentage of estimated shipments. The percentage of the total number of shares subject to options or awards granted in a single fiscal year; this will take effect only if the percentage is less than a specified amount in the plan contract. Weighted average remaining contractual term for option awards granted, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Aggregate dividends paid during the period for each share of special common stock outstanding. Total of all stockholders' equity (deficit) items, before ESOP and Treasury stock. Name of the equity-based compensation arrangement plan. Name of the equity-based compensation arrangement plan. 2017 Plan [Member] Information pertaining to unearned employee stock ownership plan shares. Units Delivered [Member] The increase (decrease) in vacation accrual for the period. The increase (decrease) in employee stock ownership plan payable for the period. Deferred tax liabilities as of the balance sheet date. Inventory, Net Assets, Current Assets Liabilities, Current Liabilities TotalStockholdersEquityBeforyEsopAndTreasuryStock [Default Label] Treasury Stock, Value Stockholders' Equity Attributable to Parent Liabilities and Equity Gross Profit Operating Income (Loss) Other Nonoperating Income Nonoperating Income (Expense) Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Weighted Average Number of Shares Outstanding, Basic Weighted Average Number of Shares Outstanding, Diluted Dividends, Common Stock, Cash Increase (Decrease) in Accounts Receivable Increase (Decrease) in Income Taxes Receivable Increase (Decrease) in Inventories Increase (Decrease) in Prepaid Expense and Other Assets Net Cash Provided by (Used in) Operating Activities Payments to Acquire Property, Plant, and Equipment Payments to Acquire Available-for-sale Securities Net Cash Provided by (Used in) Investing Activities Payments of Ordinary Dividends, Common Stock Payments for Repurchase of Common Stock Net Cash Provided by (Used in) Financing Activities Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term 2007 Plan [Member] [Default Label] Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Number of Shares Share-based Compensation Arrangement by Share-based Payment Award, Option, Nonvested, Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested Options Forfeited, Weighted Average Grant Date Fair Value Contract with Customer, Liability Employee Stock Ownership Plan (ESOP), Shares in ESOP