Loans - Summary of Aging of Recorded Investment in Past Due Portfolio Loans by Portfolio Class and Category (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans and Leases Receivable, Gross	$ 4,267,430	$ 4,097,050
Non-Covered Loans
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	13,697	10,828
90 or More Days Past Due	8,113	2,715
Total Past Due	21,810	13,543
Current	4,196,531	4,009,353
Loans and Leases Receivable, Gross	4,218,341	4,022,896
Total	4,219,689	4,024,221
Non-Covered Loans | Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	11,213	7,882
90 or More Days Past Due	6,020	1,770
Total Past Due	17,233	9,652
Current	2,015,696	1,909,068
Total	2,032,929	1,918,720
Non-Covered Loans | CRE - investor owned
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,362	934
90 or More Days Past Due	129	0
Total Past Due	1,491	934
Current	824,956	768,341
Total	826,447	769,275
Non-Covered Loans | CRE - owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	258	0
90 or More Days Past Due	808	0
Total Past Due	1,066	0
Current	587,979	554,589
Total	589,045	554,589
Non-Covered Loans | Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	0	76
90 or More Days Past Due	0	0
Total Past Due	0	76
Current	326,858	303,015
Total	326,858	303,091
Non-Covered Loans | Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	864	1,529
90 or More Days Past Due	1,156	945
Total Past Due	2,020	2,474
Current	306,365	338,838
Total	308,385	341,312
Non-Covered Loans | Consumer and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	0	407
90 or More Days Past Due	0	0
Total Past Due	0	407
Current	134,677	135,502
Loans and Leases Receivable, Gross	134,677	135,909
Total	$ 136,025	$ 137,234