Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Surplus	Accumulated Other Comprehensive (Loss) Income	Undivided Profits	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Undivided Profits
Balance at Dec. 31, 2019	$ 2,988,924	$ 767	$ 1,136	$ 2,117,282	$ 20,891	$ 848,848	$ (128,101)	$ (128,101)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	222,554				20,618	201,936
Stock issued for employee stock purchase plan	956		1	955
Stock-based compensation plans, net	7,395		2	7,393
Stock repurchases	(93,307)		(49)	(93,258)
Dividends on preferred stock	(39)					(39)
Dividends on common stock	(56,141)					(56,141)
Balance at Sep. 30, 2020	$ 2,942,241	767	1,090	2,032,372	41,509	866,503
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	Accounting Standards Update 2016-13 [Member]
Balance at Jun. 30, 2020	$ 2,904,703	767	1,090	2,029,383	54,310	819,153
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	53,097				(12,801)	65,898
Stock-based compensation plans, net	2,989			2,989
Dividends on preferred stock	(13)					(13)
Dividends on common stock	(18,535)					(18,535)
Balance at Sep. 30, 2020	2,942,241	767	1,090	2,032,372	41,509	866,503
Balance at Dec. 31, 2020	2,976,656	767	1,081	2,014,076	59,726	901,006
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	151,763				(71,155)	222,918
Stock issued for employee stock purchase plan	1,170		1	1,169
Stock-based compensation plans, net	13,813		3	13,810
Stock repurchases	(54,513)		(19)	(54,494)
Dividends on preferred stock	(39)					(39)
Dividends on common stock	(58,319)					(58,319)
Balance at Sep. 30, 2021	3,030,531	767	1,066	1,974,561	(11,429)	1,065,566
Balance at Jun. 30, 2021	3,039,366	767	1,084	2,021,128	12,073	1,004,314
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive (loss) income	57,072				(23,502)	80,574
Stock-based compensation plans, net	4,848			4,848
Stock repurchases	(51,433)		(18)	(51,415)
Dividends on preferred stock	(13)					(13)
Dividends on common stock	(19,309)					(19,309)
Balance at Sep. 30, 2021	$ 3,030,531	$ 767	$ 1,066	$ 1,974,561	$ (11,429)	$ 1,065,566