Note 3 - Earnings Per Share - Earnings Per Share Calculation (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Numerator for basic and diluted earnings per share – Net income available to common shareholders	$ 98,275	$ 110,227	$ 188,730	$ 202,680
Denominator for basic earnings per share – weighted average shares outstanding (in shares)	54,460	55,640	54,617	55,788
Effect of dilutive securities– Employee stock options and restricted share awards (in shares)	1,644	1,670	1,717	1,822
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	56,104	57,310	56,334	57,610
Basic earnings per common share (in dollars per share)	$ 1.80	$ 1.98	$ 3.46	$ 3.63
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 1.75	$ 1.92	$ 3.35	$ 3.52