Note 6 - Stock-Based Compensation (Details) - Stock Options Exercisable (USD $)	3 Months Ended
	Mar. 31, 2014
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Stock Options Exercisable (in Shares)	400,361
Weighted-Average Exercise Price	$ 10.72
Range 1 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Price Range	$ 5.76
Upper Price Range	$ 8.00
Stock Options Exercisable (in Shares)	181,059
Weighted-Average Exercise Price	$ 5.76
Range 2 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Price Range	$ 8.01
Upper Price Range	$ 10.00
Stock Options Exercisable (in Shares)	64,450
Weighted-Average Exercise Price	$ 9.72
Range 3 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Price Range	$ 10.01
Upper Price Range	$ 20.00
Stock Options Exercisable (in Shares)	88,116
Weighted-Average Exercise Price	$ 12.74
Range 4 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Lower Price Range	$ 20.01
Upper Price Range	$ 33.44
Stock Options Exercisable (in Shares)	66,736
Weighted-Average Exercise Price	$ 22.47