Allowance for Loan Losses - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Jul. 01, 2006
Receivables [Abstract]
Percentage of loans granted forbearance qualified as TDR	69.00%	69.00%
Criteria for loans to be considered as nonperforming (greater than)	90 days
Tier 1 of government guarantee (at least) (in percentage)	97.00%		97.00%
TDR payment default period (more than)	60 days
Period of loans past due that have accrued interest (greater than)	90 days