v3.8.0.1
Securities - Additional Information (Details)
Dec. 31, 2017
Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]    
Weighted average yield, total 5.13% 0.90%
Agency Mortgage-backed Securities    
Schedule Of Available For Sale Securities [Line Items]    
Weighted average yield, total 2.55% 2.58%