| Document And Entity Information | 3 Months Ended | |
| Mar. 30, 2014 | 1-May-14 | |
| Document And Entity Information [Abstract] | ' | ' |
| Document Type | '10-Q | ' |
| Amendment Flag | 'false | ' |
| Document Period End Date | 30-Mar-14 | ' |
| Document Fiscal Period Focus | 'Q1 | ' |
| Document Fiscal Year Focus | '2014 | ' |
| Entity Registrant Name | 'NATIONAL PRESTO INDUSTRIES INC | ' |
| Entity Central Index Key | '0000080172 | ' |
| Current Fiscal Year End Date | '--12-31 | ' |
| Entity Filer Category | 'Accelerated Filer | ' |
| Entity Common Stock, Shares Outstanding | ' | 6,909,333 |
| Entity Current Reporting Status | 'Yes | ' |
| Condensed Consolidated Balance Sheets (USD $) | Mar. 30, 2014 | Dec. 31, 2013 |
| In Thousands, unless otherwise specified | ||
| CURRENT ASSETS: | ' | ' |
| Cash and cash equivalents | $7,970 | $22,953 |
| Marketable securities | 27,707 | 36,404 |
| Accounts receivable, net | 62,754 | 84,322 |
| Inventories: | ' | ' |
| Finished goods | 36,119 | 36,078 |
| Work in process | 50,084 | 49,690 |
| Raw materials | 9,396 | 6,746 |
| Supplies | 15 | ' |
| Total inventory | 95,614 | 92,514 |
| Deferred tax assets | 8,083 | 8,083 |
| Income tax receivable | 1,504 | 213 |
| Other current assets | 19,609 | 19,584 |
| Total current assets | 223,241 | 264,073 |
| Property, Plant and equipment, gross | 164,193 | 155,872 |
| Less allowance for depreciation | 68,574 | 66,283 |
| PROPERTY, PLANT AND EQUIPMENT, NET | 95,619 | 89,589 |
| GOODWILL | 11,485 | 11,485 |
| INTANGIBLE ASSETS, net | 22,254 | 24,698 |
| NOTE RECEIVABLE | 3,725 | 3,695 |
| Total assets | 356,324 | 393,540 |
| CURRENT LIABILITIES: | ' | ' |
| Accounts payable | 31,573 | 38,323 |
| Accrued liabilities | 15,266 | 15,907 |
| Total current liabilities | 46,839 | 54,230 |
| DEFERRED INCOME TAX | 6,761 | 6,759 |
| COMMITMENTS AND CONTINGENCIES | ' | ' |
| STOCKHOLDERS' EQUITY | ' | ' |
| Common stock, $1 par value: Authorized: 12,000,000 Issued: 7,440,518 | 7,441 | 7,441 |
| Paid-in capital | 5,287 | 4,998 |
| Retained earnings | 306,631 | 336,895 |
| Accumulated other comprehensive income | 12 | 8 |
| Stockholders' Equity before Treasury Stock | 319,371 | 349,342 |
| Treasury stock, at cost | 16,647 | 16,791 |
| Total stockholders' equity | 302,724 | 332,551 |
| Total liabilities and stockholders' equity | $356,324 | $393,540 |
| Condensed Consolidated Balance Sheets (Parenthetical) (USD $) | Mar. 30, 2014 | Dec. 31, 2013 |
| Consolidated Balance Sheets [Abstract] | ' | ' |
| Common stock, par value | $1 | $1 |
| Common stock, shares authorized | 12,000,000 | 12,000,000 |
| Common stock, shares issued | 7,440,518 | 7,440,518 |
| Consolidated Statements Of Comprehensive Income (USD $) | 3 Months Ended | |||
| In Thousands, except Per Share data, unless otherwise specified | Mar. 30, 2014 | Mar. 31, 2013 | ||
| Consolidated Statements Of Comprehensive Income [Abstract] | ' | ' | ||
| Net sales | $86,554 | $83,190 | ||
| Cost of sales | 70,834 | 66,981 | ||
| Gross profit | 15,720 | 16,209 | ||
| Selling and general expenses | 6,295 | 5,684 | ||
| Intangibles amortization | 2,443 | 167 | ||
| Operating profit | 6,982 | 10,358 | ||
| Other income | 164 | 208 | ||
| Earnings before provision for income taxes | 7,146 | 10,566 | ||
| Income tax provision | 2,456 | 3,712 | ||
| Net earnings | 4,690 | 6,854 | ||
| Weighted average common shares outstanding: | ' | ' | ||
| Basic and diluted | 6,921 | 6,903 | ||
| Net earnings per share: | ' | ' | ||
| Basic and diluted | $0.68 | $0.99 | ||
| Other comprehensive income, net of tax: | ' | ' | ||
| Unrealized gain on available-for-sale securities | 4 | 8 | ||
| Comprehensive income | $4,694 | $6,862 | ||
| Cash dividends declared and paid per common share | $5.05 | [1] | $0 | [1] |
| [1] | An accelerated payment was made in late December 2012 of the annual 2013 dividend. The acceleration was occasioned by the uncertainty over the federal income tax rates that would be in effect for 2013. In contrast, the annual 2014 dividend payment was made during the first quarter of 2014. | |||
| Consolidated Statements Of Cash Flows (USD $) | 3 Months Ended | |
| In Thousands, unless otherwise specified | Mar. 30, 2014 | Mar. 31, 2013 |
| Cash flows from operating activities: | ' | ' |
| Net earnings | $4,690 | $6,854 |
| Adjustments to reconcile net earnings to net cash provided by operating activities: | ' | ' |
| Provision for depreciation | 2,337 | 2,114 |
| Intangibles amortization | 2,443 | 167 |
| Provision for doubtful accounts | 180 | 56 |
| Other | 32 | 109 |
| Changes in: | ' | ' |
| Accounts receivable | 22,886 | 25,914 |
| Inventories | 1,597 | -13,513 |
| Other current assets | 3 | -6,835 |
| Accounts payable and accrued liabilities | -8,402 | -5,088 |
| Federal and state income taxes | -1,293 | 1,043 |
| Net cash provided by operating activities | 24,473 | 10,821 |
| Cash flows from investing activities: | ' | ' |
| Marketable securities purchased | -1,208 | -1,709 |
| Marketable securities - maturities and sales | 9,912 | 2,264 |
| Acquisition of property, plant and equipment | -3,868 | -5,769 |
| Acquisition of businesses, net of cash acquired | -10,000 | ' |
| Sale of property, plant and equipment | 300 | 3 |
| Net cash used in investing activities | -4,864 | -5,211 |
| Cash flows from financing activities: | ' | ' |
| Dividends paid | -34,954 | ' |
| Other | 362 | ' |
| Net cash used in financing activities | -34,592 | ' |
| Net increase (decrease) in cash and cash equivalents | -14,983 | 5,610 |
| Cash and cash equivalents at beginning of period | 22,953 | 37,437 |
| Cash and cash equivalents at end of period | $7,970 | $43,047 |
| Business Segments (Tables) | 3 Months Ended | ||||||||||||
| Mar. 30, 2014 | |||||||||||||
| Business Segments [Abstract] | ' | ||||||||||||
| Summary Of Business Segments Information | ' | ||||||||||||
| (in thousands) | |||||||||||||
| Housewares / Small Appliances | Defense Products | Absorbent Products | Total | ||||||||||
| Quarter ended March 30, 2014 | |||||||||||||
| External net sales | $ | 19,363 | $ | 48,289 | $ | 18,902 | $ | 86,554 | |||||
| Gross profit | 3,789 | 11,305 | 626 | 15,720 | |||||||||
| Operating profit | 944 | 6,027 | 11 | 6,982 | |||||||||
| Total assets | 125,828 | 164,334 | 66,162 | 356,324 | |||||||||
| Depreciation and amortization | 242 | 3,108 | 1,431 | 4,781 | |||||||||
| Capital expenditures | 164 | 602 | 3,102 | 3,868 | |||||||||
| Quarter ended March 31, 2013 | |||||||||||||
| External net sales | $ | 24,889 | $ | 38,951 | $ | 19,350 | $ | 83,190 | |||||
| Gross profit | 4,457 | 10,066 | 1,686 | 16,209 | |||||||||
| Operating profit | 1,558 | 7,665 | 1,135 | 10,358 | |||||||||
| Total assets | 188,776 | 108,200 | 59,955 | 356,931 | |||||||||
| Depreciation and amortization | 282 | 681 | 1,318 | 2,281 | |||||||||
| Capital expenditures | 114 | 1,583 | 4,072 | 5,769 | |||||||||
| Cash, Cash Equivalents And Marketable Securities (Tables) | 3 Months Ended | ||||||||||||
| Mar. 30, 2014 | |||||||||||||
| Cash, Cash Equivalents And Marketable Securities [Abstract] | ' | ||||||||||||
| Summary Of The Amortized Costs And Fair Values Of Marketable Securities | ' | ||||||||||||
| (In Thousands) | |||||||||||||
| MARKETABLE SECURITIES | |||||||||||||
| Amortized Cost | Fair Value | Gross Unrealized Gains | Gross Unrealized Losses | ||||||||||
| 30-Mar-14 | |||||||||||||
| Tax-exempt Municipal Bonds | $ | 15,000 | $ | 15,018 | $ | 21 | $ | 3 | |||||
| Variable Rate Demand Notes | 12,689 | 12,689 | - | - | |||||||||
| Total Marketable Securities | $ | 27,689 | $ | 27,707 | $ | 21 | $ | 3 | |||||
| 31-Dec-13 | |||||||||||||
| Tax-exempt Municipal Bonds | $ | 20,813 | $ | 20,825 | $ | 18 | $ | 6 | |||||
| Variable Rate Demand Notes | 15,579 | 15,579 | - | - | |||||||||
| Total Marketable Securities | $ | 36,392 | $ | 36,404 | $ | 18 | $ | 6 | |||||
| Business Acquisition (Tables) | 3 Months Ended | |||||
| Mar. 30, 2014 | ||||||
| Business Acquisition [Abstract] | ' | |||||
| Summary of Assets Acquired and Liabilities Assumed in a Business Combination | ' | |||||
| (in thousands) | ||||||
| Receivables | $ | 1,498 | ||||
| Inventory | 4,697 | |||||
| Other current assets | 28 | |||||
| Property, plant and equipment | 4,800 | |||||
| Total assets acquired | 11,023 | |||||
| Less: Current liabilities assumed | 489 | |||||
| Net assets acquired | $ | 10,534 | ||||
| Summary Pro Forma Results of Operations for a Material Business Acquisition | ' | |||||
| (unaudited) | ||||||
| (in thousands, except per share data) | ||||||
| Quarter Ended | Quarter Ended | |||||
| 30-Mar-14 | 31-Mar-13 | |||||
| Net sales | $ | 87,189 | $ | 87,321 | ||
| Net earnings | 4,410 | 6,982 | ||||
| Net earnings per share (basic and diluted) | $ | 0.64 | $ | 1.01 | ||
| Weighted average shares outstanding (basic and diluted) | 6,921 | 6,903 | ||||
| Business Segments (Schedule Of Segment Information) (Details) (USD $) | 3 Months Ended | ||
| In Thousands, unless otherwise specified | Mar. 30, 2014 | Mar. 31, 2013 | Dec. 31, 2013 |
| Segment Reporting Information [Line Items] | ' | ' | ' |
| External net sales | $86,554 | $83,190 | ' |
| Gross profit | 15,720 | 16,209 | ' |
| Operating profit | 6,982 | 10,358 | ' |
| Total assets | 356,324 | 356,931 | 393,540 |
| Depreciation and amortization | 4,781 | 2,281 | ' |
| Capital expenditures | 3,868 | 5,769 | ' |
| Housewares/ Small Appliances [Member] | ' | ' | ' |
| Segment Reporting Information [Line Items] | ' | ' | ' |
| External net sales | 19,363 | 24,889 | ' |
| Gross profit | 3,789 | 4,457 | ' |
| Operating profit | 944 | 1,558 | ' |
| Total assets | 125,828 | 188,776 | ' |
| Depreciation and amortization | 242 | 282 | ' |
| Capital expenditures | 164 | 114 | ' |
| Defense Products [Member] | ' | ' | ' |
| Segment Reporting Information [Line Items] | ' | ' | ' |
| External net sales | 48,289 | 38,951 | ' |
| Gross profit | 11,305 | 10,066 | ' |
| Operating profit | 6,027 | 7,665 | ' |
| Total assets | 164,334 | 108,200 | ' |
| Depreciation and amortization | 3,108 | 681 | ' |
| Capital expenditures | 602 | 1,583 | ' |
| Absorbent Products [Member] | ' | ' | ' |
| Segment Reporting Information [Line Items] | ' | ' | ' |
| External net sales | 18,902 | 19,350 | ' |
| Gross profit | 626 | 1,686 | ' |
| Operating profit | 11 | 1,135 | ' |
| Total assets | 66,162 | 59,955 | ' |
| Depreciation and amortization | 1,431 | 1,318 | ' |
| Capital expenditures | $3,102 | $4,072 | ' |
| Cash, Cash Equivalents and Marketable Securities (Summary Of The Amortized Costs And Fair Values Of Marketable Securities) (Details) (USD $) | Mar. 30, 2014 | Dec. 31, 2013 |
| In Thousands, unless otherwise specified | ||
| Schedule of Available-for-sale Securities [Line Items] | ' | ' |
| MARKETABLE SECURITIES, Amortized Cost | $27,689 | $36,392 |
| MARKETABLE SECURITIES, Fair Value | 27,707 | 36,404 |
| MARKETABLE SECURITIES, Gross Unrealized Gains | 21 | 18 |
| MARKETABLE SECURITIES - Gross Unrealized Losses | 3 | 6 |
| Tax-Exempt Municipal Bonds [Member] | ' | ' |
| Schedule of Available-for-sale Securities [Line Items] | ' | ' |
| MARKETABLE SECURITIES, Amortized Cost | 15,000 | 20,813 |
| MARKETABLE SECURITIES, Fair Value | 15,018 | 20,825 |
| MARKETABLE SECURITIES, Gross Unrealized Gains | 21 | 18 |
| MARKETABLE SECURITIES - Gross Unrealized Losses | 3 | 6 |
| Variable Rate Demand Notes [Member] | ' | ' |
| Schedule of Available-for-sale Securities [Line Items] | ' | ' |
| MARKETABLE SECURITIES, Amortized Cost | 12,689 | 15,579 |
| MARKETABLE SECURITIES, Fair Value | $12,689 | $15,579 |
| Cash, Cash Equivalents And Marketable Securities (Narrative) (Details) (USD $) | 3 Months Ended | |
| Mar. 30, 2014 | Mar. 31, 2013 | |
| Transfers into Level 2 | $0 | ' |
| Transfers out of Level 2 | 0 | ' |
| Proceeds from sales of available-for-sale securities | 9,912,000 | 2,264,000 |
| Gross gains or losses related to sales of marketable securities | 0 | 0 |
| Net unrealized losses included in accumulated other comprehensive income, before taxes | 7,000 | 12,000 |
| Contractual maturities of marketable securities within 1 year | 12,773,000 | ' |
| Contractual maturities of marketable securities, years 2-5 | 3,330,000 | ' |
| Contractual maturities of marketable securities, years 6-10 | 4,822,000 | ' |
| Contractual maturities of marketable securities, after 10 years | 6,782,000 | ' |
| Marketable securities liquidation period | '7 days | ' |
| Accumulated Net Unrealized Investment Gain (Loss) [Member] | ' | ' |
| Reclassification out of AOCI | $0 | $0 |
| Business Acquisition (Schedule of Assets Acquired and Liabilities Assumed) (Details) (Tech Ord [Member], USD $) | Jan. 24, 2014 |
| In Thousands, unless otherwise specified | |
| Tech Ord [Member] | ' |
| Business Acquisition [Line Items] | ' |
| Receivables | $1,498 |
| Inventory | 4,697 |
| Other Current Assets | 28 |
| Property, Plant and Equipment | 4,800 |
| Total Assets Acquired | 11,023 |
| Less: Current Liabilities Assumed | 489 |
| Net Assets Acquired | $10,534 |
| Business Acquisition (Schedule of Pro Forma Results of Operatiaons) (Details) (USD $) | 3 Months Ended | |
| In Thousands, except Per Share data, unless otherwise specified | Mar. 30, 2014 | Mar. 31, 2013 |
| Business Acquisition [Line Items] | ' | ' |
| Basic and diluted | 6,921 | 6,903 |
| Tech Ord [Member] | ' | ' |
| Business Acquisition [Line Items] | ' | ' |
| Pro Forma Net Sales | 87,189 | 87,321 |
| Pro Forma Net Earnings | 4,410 | 6,982 |
| Net earnings per share (basic and diluted) | 0.64 | 1.01 |
| Basic and diluted | 6,921 | 6,903 |
| Business Acquisition (Narrative) (Details) (USD $) | 3 Months Ended | 1 Months Ended | 3 Months Ended | ||
| In Thousands, unless otherwise specified | Mar. 30, 2014 | Mar. 31, 2013 | Jan. 24, 2014 | Mar. 30, 2014 | Jun. 29, 2014 |
| Tech Ord [Member] | Tech Ord [Member] | Tech Ord [Member] | |||
| Scenario, Forecast [Member] | |||||
| Business Acquisition [Line Items] | ' | ' | ' | ' | ' |
| Net sales | $86,554 | $83,190 | ' | ' | ' |
| Business Combination, Consideration Transferred | ' | ' | 10,534 | ' | ' |
| Cash Paid to Acquire Business | ' | ' | 10,000 | ' | 534 |
| Estimated Amount of Acquired Receivable Uncollectible | ' | ' | 20 | ' | ' |
| Revenue of Acquiree Included in Conolidated Income Statement Since Acquisition Date | ' | ' | ' | 2,015 | ' |
| Earnings (Loss) of Acquiree Included in Conolidated Income Statement Since Acquisition Date | ' | ' | ' | $155 | ' |
