Short-Term Borrowings and Long-Term Debt - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Debt Disclosure [Line Items]
Interest expense, debt	$ 5,817,000	$ 6,270,000	$ 11,611,000	$ 12,626,000
Weighted average interest rates associated with short-term borrowings	0.07%		0.07%
Federal Home Loan Bank Advances | San Francisco
Debt Disclosure [Line Items]
Market value of collateral pledged	1,400,000,000		1,400,000,000
Federal Reserve Bank Advances
Debt Disclosure [Line Items]
Market value of collateral pledged	$ 626,000,000		$ 626,000,000