Purchased Credit Impaired ("PCI") Loans - Summary of PCI Loans by Category (Details) - Covered Loans $ in Thousands	Dec. 31, 2018 USD ($) rating	Dec. 31, 2017 USD ($) rating
Covered Loans [Line Items]
Recorded Investment PCI Loans	$ 46,401	$ 74,154
Commercial and industrial
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.09	6.38
Recorded Investment PCI Loans	$ 2,159	$ 3,212
CRE - investor owned
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	7.19	7.36
Recorded Investment PCI Loans	$ 23,939	$ 42,887
CRE - owner occupied
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	7.39	6.48
Recorded Investment PCI Loans	$ 9,669	$ 11,332
Construction and land development
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.03	5.99
Recorded Investment PCI Loans	$ 4,548	$ 5,883
Residential real estate
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	6.40	5.99
Recorded Investment PCI Loans	$ 6,082	$ 10,781
Total real estate loans
Covered Loans [Line Items]
Recorded Investment PCI Loans	$ 44,238	$ 70,883
Consumer and other
Covered Loans [Line Items]
Weighted- Average Risk Rating1 | rating	2.18	2.84
Recorded Investment PCI Loans	$ 4	$ 59