Note 4 - 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, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2021
Numerator for basic and diluted earnings per share – Net income available to common shareholders	$ 110,227	$ 58,044	$ 202,680	$ 103,377
Basic (in shares)	55,640	56,009	55,788	55,819	55,819
Employee stock options and restricted stock awards (in shares)	1,670	1,947	1,822	2,027
Denominator for diluted earnings per share – adjusted weighted average shares outstanding and assumed conversions (in shares)	57,310	57,956	57,610	57,846	57,846
Basic earnings per common share (in dollars per share)	$ 1.98	$ 1.04	$ 3.63	$ 1.85
Diluted earnings per common share and common share equivalents (in dollars per share)	$ 1.92	$ 1.00	$ 3.52	$ 1.79