Segment Reporting - Schedule of Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net interest income	$ 43,610	$ 27,617	$ 104,288	$ 81,918
Provision for loan losses	(784)	71	(1,906)	(727)
Mortgage banking income	32,227	36,938	89,887	91,574
Change in fair value of mortgage servicing rights	(893)		(3,234)
Other noninterest income	6,486	7,024	17,911	21,779
Depreciation and amortization	1,097	972	3,090	2,994
Amortization of intangibles	558	526	1,073	1,605
Amortization and impairment of mortgage servicing rights		5,198		14,310
Loss on sale of mortgage servicing rights			249
Other noninterest mortgage banking expense	25,848	25,794	73,007	62,583
Other noninterest expense	41,721	23,039	87,358	65,979
Income before income taxes	12,990	15,979	45,981	48,527
Income tax expense	4,602	14,772	16,601	16,946
Net income	8,388	1,207	29,380	31,581
Total assets	4,581,943	3,187,180	4,581,943	3,187,180	$ 3,276,881
Goodwill	138,910	46,867	138,910	46,867	$ 46,867
Banking Segment
Segment Reporting Information [Line Items]
Net interest income	43,741	28,158	103,596	83,389
Provision for loan losses	(784)	71	(1,906)	(727)
Mortgage banking income	7,498	8,878	20,282	22,237
Other noninterest income	6,486	7,024	17,911	21,779
Depreciation and amortization	972	927	2,697	2,729
Amortization of intangibles	558	526	1,073	1,605
Other noninterest mortgage banking expense	6,216	7,293	16,420	15,223
Other noninterest expense	41,721	23,039	87,358	65,979
Income before income taxes	9,042	12,204	36,147	42,596
Total assets	4,056,901	2,661,116	4,056,901	2,661,116
Goodwill	138,810	46,767	138,810	46,767
Mortgage Segment
Segment Reporting Information [Line Items]
Net interest income	(131)	(541)	692	(1,471)
Mortgage banking income	24,729	28,060	69,605	69,337
Change in fair value of mortgage servicing rights	(893)		(3,234)
Depreciation and amortization	125	45	393	265
Amortization and impairment of mortgage servicing rights		5,198		14,310
Loss on sale of mortgage servicing rights			249
Other noninterest mortgage banking expense	19,632	18,501	56,587	47,360
Income before income taxes	3,948	3,775	9,834	5,931
Total assets	525,042	526,064	525,042	526,064
Goodwill	$ 100	$ 100	$ 100	$ 100