Reserves on Deposit with the Federal Reserve Bank and Federal Bank Stock Average Required Reserve Balances (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Reserves on Deposit with the Federal Reserve Bank and Federal Bank Stock [Abstract]
Average required reserve balances at FRB San Francisco	$ 278,101	$ 168,387