Portfolio Loans - Summary of Recorded Investment in Portfolio Loans by Class and Category Based on Impairment Method (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Loans - Ending balance:
Loans, including unearned loan fees	$ 4,350,001	$ 4,097,050
Non-Covered Loans
Balance December 31, 2018
Individually evaluated for impairment	4,453	2,579
Collectively evaluated for impairment	37,842	35,587
Total	42,295	38,166	$ 37,565	$ 33,441
Loans - Ending balance:
Individually evaluated for impairment	18,071	17,175
Collectively evaluated for impairment	4,285,529	4,005,721
Loans, including unearned loan fees	4,303,600	4,022,896
Total	4,305,626	4,024,221
Non-Covered Loans | Commercial and industrial
Balance December 31, 2018
Individually evaluated for impairment	4,266	2,508
Collectively evaluated for impairment	24,773	23,898
Total	29,039	26,406	26,996	22,056
Loans - Ending balance:
Individually evaluated for impairment	12,950	12,665
Collectively evaluated for impairment	2,108,058	1,906,055
Total	2,121,008	1,918,720
Non-Covered Loans | CRE - investor owned
Balance December 31, 2018
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	4,683	3,890
Total	4,683	3,890	3,420	3,484
Loans - Ending balance:
Individually evaluated for impairment	398	422
Collectively evaluated for impairment	843,330	768,853
Total	843,728	769,275
Non-Covered Loans | CRE - owner occupied
Balance December 31, 2018
Individually evaluated for impairment	109	71
Collectively evaluated for impairment	4,130	3,237
Total	4,239	3,308	2,890	2,969
Loans - Ending balance:
Individually evaluated for impairment	2,135	1,975
Collectively evaluated for impairment	602,363	552,614
Total	604,498	554,589
Non-Covered Loans | Construction and land development
Balance December 31, 2018
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1,987	1,487
Total	1,987	1,487	1,304	1,704
Loans - Ending balance:
Individually evaluated for impairment	0	136
Collectively evaluated for impairment	330,097	302,955
Total	330,097	303,091
Non-Covered Loans | Residential real estate
Balance December 31, 2018
Individually evaluated for impairment	52	0
Collectively evaluated for impairment	1,564	2,237
Total	1,616	2,237	2,023	1,796
Loans - Ending balance:
Individually evaluated for impairment	2,277	1,602
Collectively evaluated for impairment	296,667	339,710
Total	298,944	341,312
Non-Covered Loans | Consumer and other
Balance December 31, 2018
Individually evaluated for impairment	26	0
Collectively evaluated for impairment	705	838
Total	731	838	$ 932	$ 1,432
Loans - Ending balance:
Individually evaluated for impairment	311	375
Collectively evaluated for impairment	105,014	135,534
Loans, including unearned loan fees	105,325	135,909
Total	$ 107,351	$ 137,234