NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	$ 10,498,113,000	$ 10,288,426,000
Unearned fees, premiums and discounts, net	(19,034,000)	(16,762,000)
Allowance for non-covered loans receivable	(214,253,000)	(209,876,000)
Non-covered loans receivable, excluding covered loans, net	10,264,826,000	10,061,788,000
Accrued interest on covered and non-covered loans receivable	72,500,000	68,500,000
Covered and non-covered loans receivable pledged to secure borrowings from the FHLB and the Federal Reserve Bank	8,700,000,000	8,650,000,000
Residential
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	2,869,876,000	2,729,803,000
Ratio of mortgage loans with variable payment option features to total mortgage loans within same portfolio category (as a percent)	1.00%	1.00%
Residential | Minimum
Non-Covered loans receivable disclosures
Number of units of residential property securing fixed and adjustable rate first mortgage loans	1
Residential | Maximum
Non-Covered loans receivable disclosures
Number of units of residential property securing fixed and adjustable rate first mortgage loans	4
Residential | Single-family
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	1,953,123,000	1,796,635,000
New first mortgage loans originated	220,400,000	136,500,000
Ratio of mortgage loans with interest-only features to total mortgage loans within same portfolio category (as a percent)	1.00%	1.00%
Residential | Multifamily
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	916,753,000	933,168,000
New first mortgage loans originated	17,200,000	15,400,000
Residential | Multifamily | Minimum
Non-Covered loans receivable disclosures
Adjustable rate mortgage, term of initial fixed interest rates	6 months
Residential | Multifamily | Midrange
Non-Covered loans receivable disclosures
Adjustable rate mortgage, term of initial fixed interest rates	3 years
Residential | Multifamily | Maximum
Non-Covered loans receivable disclosures
Adjustable rate mortgage, term of initial fixed interest rates	5 years
Commercial Real Estate ("CRE")
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	3,776,874,000	3,832,365,000
Commercial Real Estate ("CRE") | Income producing
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	3,454,641,000	3,487,866,000
Commercial Real Estate ("CRE") | Construction
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	152,579,000	171,410,000
Commercial Real Estate ("CRE") | Land
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	169,654,000	173,089,000
Commercial and Industrial ("C&I")
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	3,238,605,000	3,142,472,000
Commercial and Industrial ("C&I") | Commercial Business
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	2,785,971,000	2,655,917,000
Commercial and Industrial ("C&I") | Trade finance
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	452,634,000	486,555,000
Consumer
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	612,758,000	583,786,000
Consumer | Student loans
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	341,966,000	306,325,000
Consumer | Other Consumer
Non-Covered loans receivable disclosures
Loans receivable, excluding covered loans, gross	$ 270,792,000	$ 277,461,000