Short-Term Borrowings and Long-Term Debt - Additional Information (Detail) (USD $)	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Debt Disclosure [Line Items]
Interest expense, debt	$ 5,794,000	$ 6,356,000
Weighted average interest rates associated with short-term borrowings	0.12%
Federal Home Loan Bank Advances \| San Francisco
Debt Disclosure [Line Items]
Market value of collateral pledged	1,500,000,000
Federal Reserve Bank Advances
Debt Disclosure [Line Items]
Market value of collateral pledged	$ 673,000,000

Aggregate amount of interest expense on all borrowings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher OTS

-Name Federal Regulation (FR)

-Number Title 12

-Section 563c.102

-Paragraph 8

-Chapter V

-Subsection I

-LegacyDoc This is a non-GAAP reference that was included in the 2009 taxonomy. It will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.7,8)

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Name:	us-gaap_InterestExpenseBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration