Note 2 - Summary of Significant Accounting Policies - Basic and Diluted Earnings Per Share Computation (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted average basic shares outstanding (in shares)	109,987	112,474	115,677
Effect of common stock equivalents (in shares)	1,062	887	1,051
Weighted average shares outstanding – diluted (in shares)	111,049	113,361	116,728