Note 10 - Equity Plans (Details Textual) - USD ($)				12 Months Ended
	Mar. 01, 2015	Mar. 01, 2014	Jan. 02, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jan. 31, 1994
Restricted Stock Units (RSUs) [Member] | Five Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested				$ 25,000
Restricted Stock Units (RSUs) [Member] | Ten Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested				50,000
Restricted Stock Units (RSUs) [Member] | Fifteen Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested				75,000
Restricted Stock Units (RSUs) [Member] | Twenty Five Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested				100,000
Restricted Stock Units (RSUs) [Member] | Twenty Year Anniversary [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Aggregate Intrinsic Value, Vested				$ 100,000
Restricted Stock Units (RSUs) [Member] | Supplemental Employee Retirement Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				47,639	21,506	28,341
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement By Share-based Payment Award Equity Instruments Other Than Options Converted into Shares Intrinsic Value				$ 0	$ 0
Employee Stock Option [Member] | Stock Option Plan (Option Plan) [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				180 days
Employee Stock Option [Member] | Stock Option Plan (Option Plan) [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				5 years
Employee Stock Option [Member] | Stock Option Plan (Option Plan) [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period				10 years
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period			1,800
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period				1 year
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	4,639	2,544
Match [Member]
Shares Matched				9,000	9,875	8,500
Stock Option Plan (Option Plan) [Member]
Common Stock, Capital Shares Reserved for Future Issuance							1,300,000
Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant				500,000
Share Price	$ 15.09	$ 27.51	$ 23.41
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period				0	7,000	11,667
Proceeds from Stock Options Exercised					$ 86,000	$ 86,000
Restricted Stock Units Units Number Converted						0
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value					103,000	$ 218,000
Deferred Tax Expense from Stock Options Exercised					$ 40,000	$ 83,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period				69,771
ShareBased Compensation Arrangement by ShareBased Payment Award Minimum Number of Shares Per Employee				750
Sharebased Compensation Arrangement bySharebasedPaymentAwardMatchingPurchaseRequirement				500
Sharebased Compensation Arrangement by Sharebased Payment Award Award Match				250