Note 18 - Stockholders' Equity (Details Textual) - USD ($) $ in Thousands	3 Months Ended		4 Months Ended	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Aug. 05, 2021	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	[1]	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Stockholders' Equity Attributable to Parent, Ending Balance	$ 2,463,291	$ 2,374,723		$ 2,463,291	$ 2,374,723	$ 2,452,357		$ 2,418,144	$ 2,342,448	$ 2,294,283
Stockholders' Equity, Period Increase (Decrease), Total				45,100
Net Income (Loss) Attributable to Parent, Total	72,397	56,794		222,980	157,967
Share-based Payment Arrangement, Noncash Expense, Total				4,100
Proceeds from Issuance of Common Stock, Dividend Reinvestment Plan				2,619	2,573
Treasury Stock, Value, Acquired, Cost Method	37,139		$ 74,900	100,668	12,880
Dividends, Common Stock, Cash	24,137	24,682		73,335	74,014
Other Comprehensive Income (Loss), Net of Tax, Total	$ (2,740)	$ (1,964)		$ (5,678)	$ 4,087

[1] Balance sheet amounts previously reported for the impact of the initial adoption of CECL on January 1, 2021 have been corrected. The correction had an after-tax decrease to the cumulative effect of the change in accounting principle related to ASC326 of $2.3 million.