CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - UNAUDITED - USD ($) $ in Thousands	Total	Revision of Prior Period, Accounting Standards Update, Adjustment	Common Stock	Additional Paid-In Capital	Retained Earnings	Retained Earnings Revision of Prior Period, Accounting Standards Update, Adjustment	Accumulated Other Comprehensive Income/ (Loss)
Balance at beginning of period at Dec. 31, 2019	$ 1,132,974	$ (2,223)	$ 34,970	$ 586,622	$ 515,714	$ (2,223)	$ (4,332)
Net income	9,987				9,987
Other comprehensive loss, net of tax	10,676						10,676
Total other comprehensive income	20,663
Common stock dividends	(10,544)				(10,544)
Stock compensation expense	754			754
Stock option plan	122		6	116
Employee stock purchase plan	290		9	281
Common stock repurchase	(25,702)		(820)	(24,882)
Balance at end of period at Mar. 31, 2020	1,116,334		34,165	562,891	512,934		6,344
Balance at beginning of period at Dec. 31, 2020	1,469,955		47,057	846,922	557,271		18,705
Net income	75,464				75,464
Other comprehensive loss, net of tax	(21,357)						(21,357)
Total other comprehensive income	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, net	(205)		8	(213)
Balance at end of period at Mar. 31, 2021	$ 1,511,694		$ 47,187	$ 849,606	$ 617,553		$ (2,652)