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	75,464			75,464
Other comprehensive loss, net of tax	(21,357)				(21,357)
Total other comprehensive loss	54,107
Common stock dividends	(15,182)			(15,182)
Stock compensation expense	947		947
Stock option plan	1,531	102	1,429
Employee stock purchase plan	541	20	521
Restricted stock vesting, net of tax withholding	(205)	8	(213)
Balance at end of period at Mar. 31, 2021	1,511,694	47,187	849,606	617,553	(2,652)
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	43,935			43,935
Other comprehensive loss, net of tax	(60,732)				(60,732)
Total other comprehensive loss	(16,797)
Common stock dividends	(15,615)			(15,615)
Stock compensation expense	1,472		1,472
Stock option plan	195	9	186
Employee stock purchase plan	436	10	426
Restricted stock vesting, net of tax withholding	(460)	25	(485)
Balance at end of period at Mar. 31, 2022	$ 1,488,910	$ 45,163	$ 752,671	$ 760,347	$ (69,271)