Note 7 - Stockholders' Equity and Stock-based Compensation Expense (Details Textual) - USD ($) $ in Millions		3 Months Ended	6 Months Ended
		Jun. 30, 2016	Jun. 30, 2016	Feb. 08, 2016
Modified Stock Buyback Program [Member]
Stock Repurchase Program, Remaining Authorized Repurchase Amount		$ 7.1	$ 7.1	$ 10.0
Stock Repurchased During Period, Shares		250,805	278,818
Treasury Stock, Value, Acquired, Cost Method		$ 2.6	$ 2.9
Two Thousand Four Equity Incentive Plan [Member] | Fungible Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award Shares Available For Grant In Period Gross			416,474
Two Thousand Four Equity Incentive Plan [Member] | Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			196,450
Two Thousand Four Equity Incentive Plan [Member]
Number of Stock Awards Counted for Every Share Granted or Canceled			2.12
Share Based Compensation Arrangement By Share Based Payment Award Shares Available For Grant In Period Gross			925,675
Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period		306,237	450,549
Employee Stock Option [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized		$ 4.8	$ 4.8
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition			1 year 343 days
Share Based Compensation Arrangement By Share Based Payment Award Shares Available For Grant In Period Gross	[1],[2]		925,675

[1] Included in 'Stock awards granted' of 925,675, was 416,474 fungible shares relating to 196,450 of PSUs granted. These PSUs will result in a higher or lower number of shares of common stock that may be paid out on March 15, 2017, based on the achievement of three performance goals at targets that were pre-determined by the Board and disclosed in a Form 8-K on February 8, 2016.

[2] The Company has a "fungible share" provision in its 2004 Equity Incentive Plan whereby for each full-value award (RSU/PSU) issued or canceled under the Plan, results in a requirement to subtract / add back 2.12 shares from / to the Shares Available for Grant.