Note 1 - Summary of Significant Accounting Policies - Fair Value Assumptions (Details) - Employee Stock Option [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Expected volatility	29.70%
Expected dividends	$ 0	$ 0	$ 0
Risk-free interest rate	0.90%
Exercise price (in dollars per share)	$ 22.02
Expected term (in years) (Year)	5 years	5 years
Weighted-average grant-date fair value (in dollars per share)	$ 6.11	$ 6.04	$ 7.24
Minimum [Member]
Expected volatility		31.50%	32.80%
Expected dividends
Risk-free interest rate		1.00%	0.70%
Exercise price (in dollars per share)		$ 19.97	$ 22.55
Expected term (in years) (Year)			3 years 292 days
Weighted-average grant-date fair value (in dollars per share)
Maximum [Member]
Expected volatility		32.30%	37.90%
Risk-free interest rate		1.20%	0.90%
Exercise price (in dollars per share)		$ 22.36	$ 25.48
Expected term (in years) (Year)			5 years
Weighted-average grant-date fair value (in dollars per share)