Purchased Credit Impaired ("PCI") Loans - Summary of PCI Loans by Category (Details) - Covered Loans $ in Thousands	Mar. 31, 2018 USD ($) rating	Dec. 31, 2017 USD ($) rating
Covered Loans [Line Items]
Recorded Investment PCI Loans	$ 66,606	$ 74,154
Construction and land development
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.04	5.99
Recorded Investment PCI Loans	$ 5,553	$ 5,883
CRE - investor owned
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	7.26	7.36
Recorded Investment PCI Loans	$ 37,137	$ 42,887
CRE - owner occupied
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.39	6.48
Recorded Investment PCI Loans	$ 10,886	$ 11,332
Residential real estate
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.02	5.99
Recorded Investment PCI Loans	$ 10,008	$ 10,781
Commercial and industrial
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.35	6.38
Recorded Investment PCI Loans	$ 2,966	$ 3,212
Consumer and other
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	2.76	2.84
Recorded Investment PCI Loans	$ 56	$ 59