Portfolio Loans - Summary of Recorded Investment in Portfolio Loans by Class and Category Based on Impairment Method (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Loans - Ending balance:
Loans, including unearned loan fees	$ 4,097,050	$ 3,158,161
Non-Covered Loans
Balance December 31, 2017
Individually evaluated for impairment	2,579	3,064
Collectively evaluated for impairment	35,587	34,501
Total	38,166	37,565	$ 33,441	$ 30,185
Loans - Ending balance:
Individually evaluated for impairment	17,175	16,772
Collectively evaluated for impairment	4,005,721	3,101,620
Loans, including unearned loan fees	4,022,896	3,118,392
Total	4,024,221	3,119,154
Non-Covered Loans | Commercial and industrial
Balance December 31, 2017
Individually evaluated for impairment	2,508	2,909
Collectively evaluated for impairment	23,898	24,087
Total	26,406	26,996	22,056	16,983
Loans - Ending balance:
Individually evaluated for impairment	12,665	12,523
Collectively evaluated for impairment	1,906,055	1,620,191
Total	1,918,720	1,632,714
Non-Covered Loans | CRE - investor owned
Balance December 31, 2017
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	3,890	3,420
Total	3,890	3,420	3,484	4,382
Loans - Ending balance:
Individually evaluated for impairment	422	430
Collectively evaluated for impairment	768,853	544,378
Total	769,275	544,808
Non-Covered Loans | CRE - owner occupied
Balance December 31, 2017
Individually evaluated for impairment	71	0
Collectively evaluated for impairment	3,237	2,890
Total	3,308	2,890	2,969	3,135
Loans - Ending balance:
Individually evaluated for impairment	1,975	1,854
Collectively evaluated for impairment	552,614	348,294
Total	554,589	350,148
Non-Covered Loans | Construction and land development
Balance December 31, 2017
Individually evaluated for impairment	0	155
Collectively evaluated for impairment	1,487	1,149
Total	1,487	1,304	1,704	1,715
Loans - Ending balance:
Individually evaluated for impairment	136	1,903
Collectively evaluated for impairment	302,955	192,639
Total	303,091	194,542
Non-Covered Loans | Residential real estate
Balance December 31, 2017
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	2,237	2,023
Total	2,237	2,023	1,796	2,830
Loans - Ending balance:
Individually evaluated for impairment	1,602	62
Collectively evaluated for impairment	339,710	240,698
Total	341,312	240,760
Non-Covered Loans | Consumer and other
Balance December 31, 2017
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	838	932
Total	838	932	$ 1,432	$ 1,140
Loans - Ending balance:
Individually evaluated for impairment	375	0
Collectively evaluated for impairment	135,534	155,420
Loans, including unearned loan fees	135,909	155,420
Total	$ 137,234	$ 156,182