Note N - Stockholders' Equity (Details Textual) - USD ($)											3 Months Ended			6 Months Ended		12 Months Ended	106 Months Ended	204 Months Ended
	Oct. 30, 2018	Aug. 03, 2018	Jun. 22, 2018	Jun. 08, 2018	May 31, 2018	Jan. 04, 2018	Dec. 20, 2017	Nov. 01, 2017	Mar. 27, 2015	Mar. 10, 2015	Sep. 23, 2018	Jun. 24, 2018	Sep. 24, 2017	Sep. 23, 2018	Sep. 24, 2017	Mar. 25, 2018	Sep. 23, 2018	Sep. 23, 2018	Mar. 11, 2016	Jun. 05, 2013
Common Stock, Dividends, Amount per Annum					$ 1
Common Stock, Dividends, Amount per Quarter					$ 0.25
Common Stock, Dividends, Per Share, Declared		$ 0.25		$ 0.25							$ 0.25		$ 0	$ 0.50
Payments of Ordinary Dividends, Common Stock														$ 2,244,000	$ 125,000
Minimum Percentage of Common Stock Acquired by a Person or Group which Triggers Exercise of New Rights																				15.00%
New Right Purchase Price																				$ 100
Treasury Stock, Shares, Acquired														0				5,127,373
Treasury Stock, Value, Acquired, Cost Method																		$ 77,303,000
Common Stock, Dividends, Per Share, Cash Paid			$ 0.25
Sixth Stock Repurchase Plan [Member]
Treasury Stock, Shares, Acquired																	939,742
Treasury Stock, Value, Acquired, Cost Method																	$ 29,641,000
Stock Repurchase Program, Number of Shares Authorized to be Repurchased																			1,200,000
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased											260,258			260,258			260,258	260,258
Common Stock Purchase Rights [Member]
Common Stock, Capital Shares Reserved for Future Issuance											5,165,171			5,165,171			5,165,171	5,165,171
Subsequent Event [Member]
Common Stock, Dividends, Per Share, Declared	$ 0.25
Ordinary Cash Dividends [Member]
Payments of Ordinary Dividends, Common Stock														$ 2,094,000
Special Cash Dividend [Member]
Common Stock, Dividends, Per Share, Declared							$ 5	$ 5	$ 25	$ 25
Payments of Ordinary Dividends, Common Stock						$ 20,923,000			$ 115,100,000
Special Cash Dividends on Restricted Stock Declared on November 1, 2017 [Member]
Payments of Ordinary Dividends, Common Stock												$ 25,000
Dividends Payable								$ 25,000
Special Cash Dividends on Restricted Stock Declared on March 10, 2015 [Member]
Payments of Ordinary Dividends, Common Stock												$ 125,000				$ 875,000
Dividends Payable									$ 1,000,000