CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - UNAUDITED - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Retained Earnings	Accumulated Other Comprehensive Income/ (Loss)
Balance at beginning of period at Dec. 31, 2020	$ 1,469,955	$ 47,057	$ 846,922	$ 557,271	$ 18,705
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	189,703			189,703
Other comprehensive loss, net of tax	(19,831)				(19,831)
Total comprehensive loss	169,872
Common stock dividends	(45,673)			(45,673)
Stock compensation expense	3,640		3,640
Stock option plan	2,583	193	2,390
Employee stock purchase plan	1,581	49	1,532
Restricted stock vesting, net of tax withholding	(1,577)	82	(1,659)
Repurchase of common stock	(54,321)	(1,262)	(53,059)
Balance at end of period at Sep. 30, 2021	1,546,060	46,119	799,766	701,301	(1,126)
Balance at beginning of period at Jun. 30, 2021	1,562,280	47,313	850,555	659,578	4,834
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	56,976			56,976
Other comprehensive loss, net of tax	(5,960)				(5,960)
Total comprehensive loss	51,016
Common stock dividends	(15,253)			(15,253)
Stock compensation expense	1,331		1,331
Stock option plan	567	53	514
Employee stock purchase plan	479	11	468
Restricted stock vesting, net of tax withholding	(39)	4	(43)
Repurchase of common stock	(54,321)	(1,262)	(53,059)
Balance at end of period at Sep. 30, 2021	1,546,060	46,119	799,766	701,301	(1,126)
Balance at beginning of period at Dec. 31, 2021	1,519,679	45,119	751,072	732,027	(8,539)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	132,319			132,319
Other comprehensive loss, net of tax	(134,531)				(134,531)
Total comprehensive loss	(2,212)
Common stock dividends	(46,297)			(46,297)
Stock compensation expense	6,211		6,211
Stock option plan	276	13	263
Employee stock purchase plan	1,337	32	1,305
Restricted stock vesting, net of tax withholding	(2,145)	105	(2,250)
Repurchase of common stock	(24,987)	(625)	(24,362)
Balance at end of period at Sep. 30, 2022	1,451,862	44,644	732,239	818,049	(143,070)
Balance at beginning of period at Jun. 30, 2022	1,477,169	44,630	730,285	799,707	(97,453)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	33,584			33,584
Other comprehensive loss, net of tax	(45,617)				(45,617)
Total comprehensive loss	(12,033)
Common stock dividends	(15,242)			(15,242)
Stock compensation expense	1,561		1,561
Stock option plan	36	3	33
Employee stock purchase plan	407	10	397
Restricted stock vesting, net of tax withholding	(36)	1	(37)
Balance at end of period at Sep. 30, 2022	$ 1,451,862	$ 44,644	$ 732,239	$ 818,049	$ (143,070)