Reserves on Deposit with the Federal Reserve Bank and Federal Bank Stock - Average Required Reserve Balances (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Reserves on Deposit with the Federal Reserve Bank and Federal Bank Stock [Abstract]
Average required reserve balances at FRB San Francisco	$ 455,866	$ 397,235