Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 133,148	$ 134,476	$ 137,862	$ 137,094	$ 137,105	$ 117,795	$ 106,574	$ 100,380	$ 542,580	$ 461,854	$ 374,750
Interest expense	24,263	25,651	25,062	23,947	21,648	18,356	14,185	11,140	98,923	65,329	37,853
Net interest income	108,885	108,825	112,800	113,147	115,457	99,439	92,389	89,240	443,657	396,525	336,897
Provision for loan losses	2,950	1,700	900	1,500	1,000	2,250	1,810	1,750	7,050	6,810	7,550
Noninterest income	37,456	37,953	41,960	35,885	36,374	38,053	35,581	33,953	153,254	143,961	132,140
Noninterest expense	95,552	96,500	93,290	88,832	93,313	94,746	79,026	77,944	374,174	345,029	301,618
Income before income taxes	47,839	48,578	60,570	58,700	57,518	40,496	47,134	43,499	215,687	188,647	159,869
Income taxes	9,424	11,132	13,945	13,590	13,098	8,532	10,424	9,673	48,091	41,727	67,681
Net income	$ 38,415	$ 37,446	$ 46,625	$ 45,110	$ 44,420	$ 31,964	$ 36,710	$ 33,826	$ 167,596	$ 146,920	$ 92,188
Basic earnings per share (usd per share)	$ 0.67	$ 0.65	$ 0.80	$ 0.77	$ 0.76	$ 0.61	$ 0.74	$ 0.69	$ 2.89	$ 2.80	$ 1.97
Diluted earnings per share (usd per share)	$ 0.67	$ 0.64	$ 0.80	$ 0.77	$ 0.76	$ 0.61	$ 0.74	$ 0.68	$ 2.88	$ 2.79	$ 1.96