CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-in Capital	Retained Earnings	Accumulated Other Comp. Income (Loss), net	Accounting Standards Update 2016-13	Accounting Standards Update 2016-13 Retained Earnings
Common Stock, Dividends, Per Share, Cash Paid	$ 0.16
Balance at Dec. 31, 2019	$ 4,355,748		$ 76,564	$ 3,064,467	$ 1,184,183	$ 30,534
Balance (in shares) at Dec. 31, 2019			76,564,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of employee common stock options & related tax benefits	5		$ 1	4
Exercise of employee common stock options and related tax benefits (in shares)			1,000
Common dividends paid	(12,442)				(12,442)
Repurchase of common stock	(50,790)		$ (1,015)	(49,775)
Repurchase of common stock (in shares)			(1,015,000)
Issuance of restricted common shares, net of forfeitures	0		$ 198	(198)
Issuance of restricted common shares, net of forfeitures (in shares)			198,000
Issuance of common stock pursuant to restricted stock unit agreement, net of shares withheld for taxes & related tax benefits	(2,468)		$ 84	(2,552)
Issuance of common stock pursuant to restricted stock unit agreement, net of shares withheld for taxes and related tax benefit (in shares)			84,000
Restricted shares withheld for taxes & related benefits	(1,958)		$ (32)	(1,926)
Restricted shares withheld for taxes (in shares)			(32,000)
Stock-based compensation expense	5,501			5,501
Net income	28,356				28,356
Cumulative effect of change in accounting principle							$ (31,796)	$ (31,796)
Other comprehensive income (loss)	94,972					94,972
Balance at Mar. 31, 2020	$ 4,385,128		$ 75,800	3,015,521	1,168,301	125,506
Balance (in shares) at Mar. 31, 2020			75,800,000
Common Stock, Dividends, Per Share, Cash Paid	$ 0.18
Balance at Dec. 31, 2020	$ 4,904,611	$ 217,126	$ 75,850	3,028,063	1,407,723	175,849
Balance (in shares) at Dec. 31, 2020			75,850,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred dividends paid	(3,798)				(3,798)
Exercise of employee common stock options & related tax benefits	304		$ 13	291
Exercise of employee common stock options and related tax benefits (in shares)			13,000
Common dividends paid	(13,902)				(13,902)
Issuance of restricted common shares, net of forfeitures	0		$ 172	(172)
Issuance of restricted common shares, net of forfeitures (in shares)			172,000
Issuance of common stock pursuant to restricted stock unit agreement, net of shares withheld for taxes & related tax benefits	(3,761)		$ 87	(3,848)
Issuance of common stock pursuant to restricted stock unit agreement, net of shares withheld for taxes and related tax benefit (in shares)			87,000
Restricted shares withheld for taxes & related benefits	(2,456)		$ (34)	(2,422)
Restricted shares withheld for taxes (in shares)			(34,000)
Stock-based compensation expense	5,399			5,399
Net income	125,428				125,428
Other comprehensive income (loss)	(52,301)					(52,301)
Balance at Mar. 31, 2021	$ 4,959,524	$ 217,126	$ 76,088	$ 3,027,311	$ 1,515,451	$ 123,548
Balance (in shares) at Mar. 31, 2021			76,088,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Preferred Stock, Dividends, Per Share, Cash Paid	$ 16.88