Business (Details)	Sep. 30, 2011	Dec. 31, 2010
Business Combination, Separately Recognized Transactions [Line Items]
Number of equity interest limited partnerships in affordable housing investments	6	6
Percentage of common stock	100.00%
Number of business trusts	5
Southern California [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	20
Northern California [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	11
New York State [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	8
Illinois [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	3
Washington State [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	3
Texas [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	2
Massachusetts [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	1
New Jersey [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	1
Hong Kong [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	1
Shanghai [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	1
Taipei [Member]
Business Combination, Separately Recognized Transactions [Line Items]
Number of branches	1