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Capital Requirements - Additional Information (Detail)
 3 Months Ended
Mar. 31, 2017
Jan. 01, 2019
Jan. 01, 2018
Jan. 01, 2017
Dec. 31, 2016
Jan. 01, 2016
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]            
Capital conservation buffer period 4 years          
Capital conservation buffer percentage 1.25%     0.625% 0.625% 0.625%
Capital conservation buffer percentage maintained at bank 5.53%       5.47%  
Scenario, Forecast [Member]            
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]            
Capital conservation buffer percentage   0.625% 0.625%