Purchased Credit Impaired ("PCI") Loans - Summary of Aging of Recorded Investment in Past Due PCI Loans by Portfolio Class and Category (Details) - Covered Loans - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	$ 5,076	$ 1,153
90 or More Days Past Due	9,333	6,404
Total Past Due	14,409	7,557
Current	108,094	38,844
Total	122,503	46,401
Commercial and industrial
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	945	0
90 or More Days Past Due	0	0
Total Past Due	945	0
Current	16,668	2,159
Total	17,613	2,159
CRE - investor owned
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,580	416
90 or More Days Past Due	1,868	88
Total Past Due	3,448	504
Current	39,500	23,435
Total	42,948	23,939
CRE - owner occupied
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	751	591
90 or More Days Past Due	6,358	6,279
Total Past Due	7,109	6,870
Current	27,917	2,799
Total	35,026	9,669
Construction and land development
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	152	0
90 or More Days Past Due	258	0
Total Past Due	410	0
Current	10,071	4,548
Total	10,481	4,548
Residential real estate
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	1,648	146
90 or More Days Past Due	849	37
Total Past Due	2,497	183
Current	13,674	5,899
Total	16,171	6,082
Consumer and other
Financing Receivable, Recorded Investment, Past Due [Line Items]
30-89 Days Past Due	0	0
90 or More Days Past Due	0	0
Total Past Due	0	0
Current	264	4
Total	$ 264	$ 4