SUMMARY OF OPERATIONS AND SIGNIFICANT ACCOUNTING POLICIES (Details)	12 Months Ended
	Dec. 31, 2012 trust	Dec. 31, 2011
Principles of Consolidation
Number of wholly owned subsidiaries that are statutory business trusts	7
Securities purchased under resale agreements ("Resale Agreements")
Resale agreement term, low end of range	1 day
Maximum term of resale agreement to be classified as cash and cash equivalents	90 days
Minimum term of resale agreement to be separately categorized	90 days
Loans receivable
Number of past due days for the loans receivable to be placed on nonaccrual status	90 days
Troubled debt restructurings
Period for which restructured loans remains on nonaccrual status, to demonstrate that the borrower can perform under the restructured terms	6 months
Other real estate owned
Maximum period of foreclosure within which sale of real estate owned will be recorded at fair value less cost of sales	3 months
FDIC percentage of reimbursement under shared loss agreements
FDIC percentage of reimbursement under shared loss agreements	80.00%
Percentage of company's liability for losses under shared loss agreements	20.00%	20.00%
Investment in affordable housing partnerships
Minimum partnership interest required for equity method of accounting (as a percent)	5.00%
California
Operations summary
Number of banking locations	95
New York
Operations summary
Number of banking locations	6
Georgia
Operations summary
Number of banking locations	4
Massachusetts
Operations summary
Number of banking locations	2
Texas
Operations summary
Number of banking locations	1
Washington
Operations summary
Number of banking locations	4
In-store
Operations summary
Number of banking locations	11
Greater China
Operations summary
Number of banking locations	3
Number of representative offices	3
Taiwan
Operations summary
Number of representative offices	1