NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 4) (USD $)	12 Months Ended
	Dec. 31, 2012 item	Dec. 31, 2011
Credit Quality Indicators
Number of grades in the risk rating system utilized by the company to rate credit risk of loans receivable	8
Maximum term for a loan to stay graded as Special Mention	6 months
Increase (decrease) in non-covered loans graded Substandard and Doubtful.	$ 27,000,000
Percentage increase (decrease) in non-covered loans graded Substandard and Doubtful	5.00%
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	11,958,873,000	10,288,426,000
Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	11,253,469,000	9,565,009,000
Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	186,560,000	177,548,000
Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	518,844,000	545,622,000
Doubtful
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross		247,000
Residential
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,088,031,000	2,729,803,000
Residential | Residential Single-family
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	2,187,323,000	1,796,635,000
Residential | Residential Single-family | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	2,163,918,000	1,768,149,000
Residential | Residential Single-family | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	5,131,000	11,239,000
Residential | Residential Single-family | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	18,274,000	17,247,000
Residential | Residential Multifamily
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	900,708,000	933,168,000
Residential | Residential Multifamily | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	781,552,000	810,458,000
Residential | Residential Multifamily | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	13,510,000	25,531,000
Residential | Residential Multifamily | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	105,646,000	97,179,000
Commercial Real Estate ("CRE")
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,894,695,000	3,832,365,000
Commercial Real Estate ("CRE") | Income producing
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,644,035,000	3,487,866,000
Commercial Real Estate ("CRE") | Income producing | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,416,142,000	3,211,386,000
Commercial Real Estate ("CRE") | Income producing | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	42,222,000	63,066,000
Commercial Real Estate ("CRE") | Income producing | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	185,671,000	213,414,000
Commercial Real Estate ("CRE") | Construction
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	121,589,000	171,410,000
Commercial Real Estate ("CRE") | Construction | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	63,008,000	109,184,000
Commercial Real Estate ("CRE") | Construction | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	16,885,000
Commercial Real Estate ("CRE") | Construction | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	41,696,000	62,226,000
Commercial Real Estate ("CRE") | Land
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	129,071,000	173,089,000
Commercial Real Estate ("CRE") | Land | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	79,085,000	125,534,000
Commercial Real Estate ("CRE") | Land | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	13,232,000	7,954,000
Commercial Real Estate ("CRE") | Land | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	36,754,000	39,601,000
Commercial and Industrial ("C&I")
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	4,231,265,000	3,142,472,000
Commercial and Industrial ("C&I") | Commercial Business
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,569,388,000	2,655,917,000
Commercial and Industrial ("C&I") | Commercial Business | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,380,212,000	2,492,904,000
Commercial and Industrial ("C&I") | Commercial Business | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	69,687,000	62,409,000
Commercial and Industrial ("C&I") | Commercial Business | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	119,489,000	100,357,000
Commercial and Industrial ("C&I") | Commercial Business | Doubtful
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross		247,000
Commercial and Industrial ("C&I") | Trade finance
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	661,877,000	486,555,000
Commercial and Industrial ("C&I") | Trade finance | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	632,617,000	467,822,000
Commercial and Industrial ("C&I") | Trade finance | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	24,778,000	7,161,000
Commercial and Industrial ("C&I") | Trade finance | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	4,482,000	11,572,000
Consumer
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	744,882,000	583,786,000
Consumer | Student loans
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	475,799,000	306,325,000
Consumer | Student loans | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	475,799,000	305,880,000
Consumer | Student loans | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross		188,000
Consumer | Student loans | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross		257,000
Consumer | Other Consumer
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	269,083,000	277,461,000
Consumer | Other Consumer | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	261,136,000	273,692,000
Consumer | Other Consumer | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	1,115,000
Consumer | Other Consumer | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	$ 6,832,000	$ 3,769,000