Consolidated Statements of Changes in Shareholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock [Member]	Capital Surplus [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance at Dec. 31, 2018	$ 1,591,453	$ 13,717	$ 309,545	$ 1,323,870	$ (55,679)
Balance (in shares) at Dec. 31, 2018		65,834,395
Net income per consolidated statements of income	33,339			33,339
Other comprehensive income (loss), net of tax	14,764				14,764
Common stock dividends paid ($0.23 per share)	(15,033)			(15,033)
Shares withheld to pay taxes, long-term incentive plan	(1,604)	$ 25	(1,629)
Shares withheld to pay taxes, long-term incentive plan (in shares)		123,821
Repurchase and retirement of common stock	(36,893)	$ (243)	(36,650)
Repurchase and retirement of common stock (in shares)		(1,168,273)
Compensation expense, long-term incentive plan	1,002		1,002
Balance at Mar. 31, 2019	1,587,028	$ 13,499	272,268	1,342,176	(40,915)
Balance (in shares) at Mar. 31, 2019		64,789,943
Balance at Dec. 31, 2019	$ 1,660,702	$ 13,376	256,400	1,414,526	(23,600)
Balance (in shares) at Dec. 31, 2019	64,200,111	64,200,111
FASB ASU 2016-13 adoption adjustment	$ (19,949)			(19,949)
Net income per consolidated statements of income	22,218			22,218
Other comprehensive income (loss), net of tax	31,298				31,298
Common stock dividends paid ($0.23 per share)	(14,706)			(14,706)
Shares withheld to pay taxes, long-term incentive plan	(1,020)	$ 17	(1,037)
Shares withheld to pay taxes, long-term incentive plan (in shares)		83,759
Repurchase and retirement of common stock	(27,538)	$ (184)	(27,354)
Repurchase and retirement of common stock (in shares)		(886,958)
Compensation expense, long-term incentive plan	1,394		1,394
Balance at Mar. 31, 2020	$ 1,652,399	$ 13,209	$ 229,403	$ 1,402,089	$ 7,698
Balance (in shares) at Mar. 31, 2020	63,396,912	63,396,912