Short-Term Borrowings and Long-Term Debt - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Debt Disclosure [Line Items]
Interest expense, debt	$ 5,747,000	$ 5,788,000	$ 17,358,000	$ 18,414,000
Weighted average interest rates associated with short-term borrowings	0.06%		0.06%
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	$ 599,000,000		$ 599,000,000