Loans - Summary of Aging of Recorded Investment in Past Due Portfolio Loans by Portfolio Class and Category (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Financing Receivable, Past Due [Line Items]
Loans and Leases Receivable, Gross	$ 5,228,014	$ 4,350,001
Non-Covered Loans
Financing Receivable, Past Due [Line Items]
30-89 Days Past Due	12,754	1,602
90 or More Days Past Due	10,497	12,158
Total Past Due	23,251	13,760
Current	5,109,140	4,289,840
Loans and Leases Receivable, Gross	5,132,391	4,303,600
Total	5,134,737	4,305,626
Non-Covered Loans | Commercial and industrial
Financing Receivable, Past Due [Line Items]
30-89 Days Past Due	6,913	66
90 or More Days Past Due	7,314	10,257
Total Past Due	14,227	10,323
Current	2,273,495	2,110,685
Total	2,287,722	2,121,008
Non-Covered Loans | CRE - investor owned
Financing Receivable, Past Due [Line Items]
30-89 Days Past Due	2,408	529
90 or More Days Past Due	2,000	127
Total Past Due	4,408	656
Current	1,243,283	843,072
Total	1,247,691	843,728
Non-Covered Loans | CRE - owner occupied
Financing Receivable, Past Due [Line Items]
30-89 Days Past Due	1,166	292
90 or More Days Past Due	0	565
Total Past Due	1,166	857
Current	659,267	603,641
Total	660,433	604,498
Non-Covered Loans | Construction and land development
Financing Receivable, Past Due [Line Items]
30-89 Days Past Due	62	6
90 or More Days Past Due	0	0
Total Past Due	62	6
Current	425,577	330,091
Total	425,639	330,097
Non-Covered Loans | Residential real estate
Financing Receivable, Past Due [Line Items]
30-89 Days Past Due	2,098	709
90 or More Days Past Due	1,183	897
Total Past Due	3,281	1,606
Current	370,881	297,338
Total	374,162	298,944
Non-Covered Loans | Consumer and other
Financing Receivable, Past Due [Line Items]
30-89 Days Past Due	107	0
90 or More Days Past Due	0	312
Total Past Due	107	312
Current	136,637	105,013
Loans and Leases Receivable, Gross	136,744	105,325
Total	$ 139,090	$ 107,351