v3.8.0.1
Regulatory Matters - Additional Information (Details) - USD ($)
$ in Millions
Dec. 31, 2017
Jan. 01, 2016
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]    
CET1 capital ratio, for capital adequacy purposes ratio 4.50%  
CET1 leverage ratio, to be well-capitalized under prompt corrective action provisions ratio 6.50%  
Capital buffer against risk weighted assets percentage   0.625%
Capital buffer against risk weighted assets increasing percentage annually 0.625%  
Capital buffer against risk weighted assets cumulative 2.50%  
FFB    
Compliance With Regulatory Capital Requirements Under Banking Regulations [Line Items]    
CET1 capital ratio, to be well-capitalized amount $ 200  
Tier 1 leverage ratio, to be well-capitalized amount 182  
Tier 1 risk-based capital ratio, to be well-capitalized amount 155  
Excess total risk-based capital ratio, to be well-capitalized amount $ 113