Purchased Credit Impaired ("PCI") Loans - Summary of PCI Loans by Category (Details) - Covered Loans $ in Thousands	Dec. 31, 2017 USD ($) rating	Dec. 31, 2016 USD ($) rating
Covered Loans [Line Items]
Recorded Investment PCI Loans	$ 74,154	$ 39,769
Commercial and industrial
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.38	5.87
Recorded Investment PCI Loans	$ 3,212	$ 3,523
CRE - investor owned
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	7.36	6.95
Recorded Investment PCI Loans	$ 42,887	$ 8,162
CRE - owner occupied
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.48	6.39
Recorded Investment PCI Loans	$ 11,332	$ 11,863
Construction and land development
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	5.99	5.80
Recorded Investment PCI Loans	$ 5,883	$ 4,365
Residential real estate
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	5.99	5.64
Recorded Investment PCI Loans	$ 10,781	$ 11,792
Total real estate loans
Covered Loans [Line Items]
Recorded Investment PCI Loans	$ 70,883	$ 36,182
Consumer and other
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	2.84	1.64
Recorded Investment PCI Loans	$ 59	$ 64