Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 180,824	$ 181,991	$ 144,122	$ 123,789	$ 129,846	$ 132,604	$ 132,414	$ 131,243	$ 630,726	$ 526,107	$ 448,423
Interest expense	12,626	15,445	13,830	14,614	16,927	20,269	21,773	19,837	56,515	78,806	55,712
Provision for credit losses	1,517	4,210	160,635	25,454	2,297	1,562	334	1,526
Noninterest income	23,194	26,758	6,898	14,475	9,801	11,430	6,324	7,681	71,325	35,236	31,027
Noninterest expense	99,939	98,579	115,970	66,631	66,216	65,336	63,936	63,577	381,119	259,065	249,905
Income tax expense (benefit)	22,800	23,949	(40,324)	5,825	13,109	15,492	14,168	15,266	12,250	58,035	42,240
Net income	$ 67,136	$ 66,566	$ (99,091)	$ 25,740	$ 41,098	$ 41,375	$ 38,527	$ 38,718	$ 60,351	$ 159,718	$ 123,340
Earnings (loss) per share:
Basic (in dollars per share)	$ 0.71	$ 0.71	$ (1.41)	$ 0.43	$ 0.69	$ 0.69	$ 0.62	$ 0.62	$ 0.75	$ 2.62	$ 2.29
Diluted (in dollars per share)	$ 0.71	$ 0.70	$ (1.41)	$ 0.43	$ 0.69	$ 0.69	$ 0.62	$ 0.62	$ 0.75	$ 2.60	$ 2.26