Note 13 - Accounting for Stock-based Compensation - Cash-settled Restricted Stock Unit Activity (Details) - Cash Settled RSUs [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Non-vested RSUs (in shares)	446,663	537,119	200,299
Non-vested RSUs, Weighted Average Grant Date Fair Value (in dollars per share)	$ 37.18	$ 36.36	$ 28.23
Granted (in shares)	233,790	121,015	416,432
Granted, Weighted Average Grant Date Fair Value (in dollars per share)	$ 34.29	$ 39.35	$ 39.12
Vested (in shares)	(146,619)	(78,033)	(47,742)
Vested, Weighted Average Grant Date Fair Value (in dollars per share)	$ 34.70	$ 33.29	$ 27.55
Cancelled (in shares)	(70,812)	(133,438)	(31,870)
Cancelled, Weighted Average Grant Date Fair Value (in dollars per share)	$ 37.55	$ 38.14	$ 32.12
Non-vested RSUs (in shares)	463,022	446,663	537,119
Non-vested RSUs, Weighted Average Grant Date Fair Value (in dollars per share)	$ 35.96	$ 37.18	$ 36.36
Non-vested RSUs, Average Intrinsic Value	$ 25,559
RSUs expected to vest in the future (in shares)	463,022
RSUs expected to vest in the future (in dollars per share)	$ 35.96
RSUs expected to vest in the future	$ 25,559