Restrictions on Cash and Due from Banks and Interest-earning Deposit Accounts - Additional Information (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Reserve requirement at Federal Reserve Bank	$ 6,600	$ 4,200
Average balances at Federal Reserve Bank	10,200	36,500
Pledging requirement for credit derivatives and SWAP agreements - cash	$ 50	$ 460