UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Retained Earnings- Substantially Restricted	Accumulated Other Compre- hensive (Loss) Income
Balance, beginning (in shares) at Dec. 31, 2021		110,687,533
Balance, beginning at Dec. 31, 2021	$ 3,177,622	$ 1,107	$ 2,338,814	$ 810,342	$ 27,359
Increase (Decrease) in Stockholders' Equity
Net income	223,525			223,525
Other comprehensive income (loss)	(522,507)				(522,507)
Cash dividends declared	(109,922)			(109,922)
Stock issuances under stock incentive plans (in shares)		79,421
Stock issuances under stock incentive plans	0	$ 1	(1)
Stock-based compensation and related taxes	3,639		3,639
Balance, ending (in shares) at Sep. 30, 2022		110,766,954
Balance, ending at Sep. 30, 2022	2,772,357	$ 1,108	2,342,452	923,945	(495,148)
Balance, beginning (in shares) at Jun. 30, 2022		110,766,287
Balance, beginning at Jun. 30, 2022	2,896,239	$ 1,108	2,341,097	881,246	(327,212)
Increase (Decrease) in Stockholders' Equity
Net income	79,338			79,338
Other comprehensive income (loss)	(167,936)				(167,936)
Cash dividends declared	(36,639)			(36,639)
Stock issuances under stock incentive plans (in shares)		667
Stock-based compensation and related taxes	1,355		1,355
Balance, ending (in shares) at Sep. 30, 2022		110,766,954
Balance, ending at Sep. 30, 2022	$ 2,772,357	$ 1,108	2,342,452	923,945	(495,148)
Balance, beginning (in shares) at Dec. 31, 2022	110,777,780	110,777,780
Balance, beginning at Dec. 31, 2022	$ 2,843,305	$ 1,108	2,344,005	966,984	(468,792)
Increase (Decrease) in Stockholders' Equity
Net income	168,611			168,611
Other comprehensive income (loss)	(31,575)				(31,575)
Cash dividends declared	(110,048)			(110,048)
Stock issuances under stock incentive plans (in shares)		101,585
Stock issuances under stock incentive plans	0	$ 1	(1)
Stock-based compensation and related taxes	$ 4,301		4,301
Balance, ending (in shares) at Sep. 30, 2023	110,879,365	110,879,365
Balance, ending at Sep. 30, 2023	$ 2,874,594	$ 1,109	2,348,305	1,025,547	(500,367)
Balance, beginning (in shares) at Jun. 30, 2023		110,873,887
Balance, beginning at Jun. 30, 2023	2,926,526	$ 1,109	2,346,422	1,009,782	(430,787)
Increase (Decrease) in Stockholders' Equity
Net income	52,445			52,445
Other comprehensive income (loss)	(69,580)				(69,580)
Cash dividends declared	(36,680)			(36,680)
Stock issuances under stock incentive plans (in shares)		5,478
Stock-based compensation and related taxes	$ 1,883		1,883
Balance, ending (in shares) at Sep. 30, 2023	110,879,365	110,879,365
Balance, ending at Sep. 30, 2023	$ 2,874,594	$ 1,109	$ 2,348,305	$ 1,025,547	$ (500,367)