Note 8 - Shareholders' Equity (Details Textual) $ / shares in Units, $ in Thousands		12 Months Ended
	Jan. 29, 2019 shares	Dec. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Feb. 13, 2009 $ / shares shares
Share Price (in dollars per share) | $ / shares		$ 57.73
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross (in shares)		193,000	184,000	250,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value (in dollars per share) | $ / shares		$ 7.50	$ 8.64	$ 10.19
Share-based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount | $		$ 2,494
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value | $		454	$ 693	$ 3,398
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value | $		$ 1,783	$ 1,735	$ 1,980
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period (in shares)		53,000	52,000	516,000
Excess Tax Deduction Exceeding Related Share-based Compensation, Operating Activities | $			$ 295	$ 1,485
Income Tax Expense (Benefit), Total | $		$ 30,518	$ 26,390	24,827
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)		13,000	10,000
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)					246,640
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share) | $ / shares					$ 50.92
Stock Issued During Period, Shares, Warrants Exercised (in shares)	50,788
Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased (in shares)		1,750,000
Additional Classes of Stock Authorized		2
Additional Classes of Stock Authorized, Shares Authorized, Per Class (in shares)		1,000,000
Common Stock, Shares Authorized (in shares)		150,000,000	150,000,000
Common Stock, Shares, Outstanding, Ending Balance (in shares)		26,866,000	26,807,000
Common Class B [Member]
Common Stock, Shares, Outstanding, Ending Balance (in shares)		0
Accounting Standards Update 2016-09 [Member]
Income Tax Expense (Benefit), Total | $		$ (0)	$ (87)	(435)
NQSO [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		3 years
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period (Year)		10 years
Restricted Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		3 years
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value | $		$ 527	$ 534	1,073
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Outstanding, Weighted Average Remaining Contractual Terms (Year)		1 year 4 months 24 days	1 year 3 months 18 days
Share-based Payment Arrangement, Expense | $		$ 610	$ 533	$ 758
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period (Year)		3 years
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized (in shares)		967,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition (Year)		1 year 9 months 18 days
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period (in shares)		0	0