Consolidated Statements of Shareholders’ Equity (unaudited) - USD ($) $ in Thousands	Total	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income (Loss), Net of Tax	Treasury Stock
Balance at beginning of period (in shares) at Dec. 31, 2020		71,753,705				2,212,224
Balance at beginning of period at Dec. 31, 2020	$ 2,647,088	$ 71,754	$ 1,913,285	$ 671,510	$ 33,505	$ (42,966)
Issuance of restricted shares (in shares)		86,075
Issuance of restricted shares	599	$ 86	513
Proceeds from exercise of stock options (in shares)		114,308
Proceeds from exercise of stock options	3,002	$ 114	2,888
Share-based compensation	1,304		1,304
Purchase of treasury shares (in shares)						28,438
Purchase of treasury shares	(1,456)					$ (1,456)
Net income	124,962			124,962
Dividends on common stock shares	(10,488)			(10,488)
Other comprehensive income (loss) during the period	(7,415)				(7,415)
Balance at end of period (in shares) at Mar. 31, 2021		71,954,088				2,240,662
Balance at end of period at Mar. 31, 2021	2,757,596	$ 71,954	1,917,990	785,984	26,090	$ (44,422)
Balance at beginning of period (in shares) at Dec. 31, 2021		72,017,126				(2,407,898)
Balance at beginning of period at Dec. 31, 2021	2,966,451	$ 72,017	1,924,813	1,006,436	15,590	$ (52,405)
Issuance of restricted shares (in shares)		145,393
Issuance of restricted shares	1,341	$ 145	1,196
Proceeds from exercise of stock options (in shares)		49,803
Proceeds from exercise of stock options	1,445	$ 50	1,395
Share-based compensation	1,298		1,298
Purchase of treasury shares (in shares)						365,340
Purchase of treasury shares	(17,234)					$ (17,234)
Net income	81,698			81,698
Dividends on common stock shares	(10,409)			(10,409)
Other comprehensive income (loss) during the period	(17,431)				(17,431)
Balance at end of period (in shares) at Mar. 31, 2022		72,212,322				(2,773,238)
Balance at end of period at Mar. 31, 2022	$ 3,007,159	$ 72,212	$ 1,928,702	$ 1,077,725	$ (1,841)	$ (69,639)