Segment Reporting - Summary of Operating Results of Segments (Details) - USD ($) $ in Thousands	3 Months Ended																12 Months Ended
	Dec. 31, 2018		Sep. 30, 2018		Jun. 30, 2018		Mar. 31, 2018		Dec. 31, 2017		Sep. 30, 2017		Jun. 30, 2017		Mar. 31, 2017		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net interest income (expense)	$ 103,146		$ 98,100		$ 95,384		$ 91,111		$ 87,911		$ 81,163		$ 82,384		$ 74,758		$ 387,741	$ 326,216	$ 279,439
Provision for credit losses	8,422		(1,365)		1,263		4,380		(4,475)		1,723		6,701		5,786		12,700	9,735	49,348
Noninterest income	21,007	[1]	23,976	[1]	24,672	[1]	24,983	[1]	25,656	[2]	27,124	[2]	22,989	[2]	24,105	[2]	94,638	99,874	88,403
Noninterest expense	72,696		61,231		62,435		61,939		66,371		56,530		56,134		54,321		258,301	233,356	220,180
Income tax expense (benefit)	10,709		15,074		8,384		10,950		36,980		17,457		13,570		12,639		45,117	80,646	32,540
Net income	32,326		$ 47,136		$ 47,974		$ 38,825		14,691		$ 32,577		$ 28,968		$ 26,117		166,261	102,353	65,774
Total assets	12,730,285								10,948,926								12,730,285	10,948,926
Banking
Segment Reporting Information [Line Items]
Net interest income (expense)																	407,674	344,987	297,701
Provision for credit losses																	12,700	9,735	49,348
Noninterest income																	47,316	51,286	45,499
Noninterest expense																	215,574	194,212	186,874
Income tax expense (benefit)																	52,464	88,417	37,442
Net income																	174,252	103,909	69,536
Total assets	12,622,287								10,854,206								12,622,287	10,854,206
Financial Services
Segment Reporting Information [Line Items]
Net interest income (expense)																	(2,307)	(1,347)	(201)
Noninterest income																	46,805	47,956	42,727
Noninterest expense																	35,679	36,178	32,334
Income tax expense (benefit)																	3,979	2,000	3,567
Net income																	4,840	8,431	6,625
Total assets	94,618								90,639								94,618	90,639
Corporate
Segment Reporting Information [Line Items]
Net interest income (expense)																	(17,626)	(17,424)	(18,061)
Noninterest income																	517	632	177
Noninterest expense																	7,048	2,966	972
Income tax expense (benefit)																	(11,326)	(9,771)	(8,469)
Net income																	(12,831)	(9,987)	$ (10,387)
Total assets	$ 13,380								$ 4,081								$ 13,380	$ 4,081

[1] Includes net securities gains (losses) of $(54) thousand, $2 thousand, $(1.8) million and $12 thousand during the fourth, third, second and first quarters of 2018, respectively.

[2] Includes net securities gains (losses) of $16 thousand, $1 thousand, $(244) thousand and $81 thousand during the fourth, third, second and first quarters of 2017, respectively