NON-COVERED LOANS AND ALLOWANCE FOR LOAN LOSSES (Details 4) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013 item	Dec. 31, 2012 item
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
Number of loss grade loans	0	0
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	$ 12,375,028	$ 11,958,873
Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	11,680,539	11,253,469
Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	207,364	186,560
Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	487,125	518,844
Residential
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,254,133	3,088,031
Residential | Residential Single-family
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	2,334,913	2,187,323
Residential | Residential Single-family | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	2,310,623	2,163,918
Residential | Residential Single-family | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	6,278	5,131
Residential | Residential Single-family | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	18,012	18,274
Residential | Residential Multifamily
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	919,220	900,708
Residential | Residential Multifamily | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	823,560	781,552
Residential | Residential Multifamily | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	11,782	13,510
Residential | Residential Multifamily | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	83,878	105,646
Commercial Real Estate ("CRE")
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,996,312	3,894,695
Commercial Real Estate ("CRE") | Income producing
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,754,434	3,644,035
Commercial Real Estate ("CRE") | Income producing | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,522,732	3,416,142
Commercial Real Estate ("CRE") | Income producing | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	54,457	42,222
Commercial Real Estate ("CRE") | Income producing | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	177,245	185,671
Commercial Real Estate ("CRE") | Construction
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	129,881	121,589
Commercial Real Estate ("CRE") | Construction | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	69,511	63,008
Commercial Real Estate ("CRE") | Construction | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	16,836	16,885
Commercial Real Estate ("CRE") | Construction | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	43,534	41,696
Commercial Real Estate ("CRE") | Land
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	111,997	129,071
Commercial Real Estate ("CRE") | Land | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	62,383	79,085
Commercial Real Estate ("CRE") | Land | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	13,139	13,232
Commercial Real Estate ("CRE") | Land | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	36,475	36,754
Commercial and Industrial ("C&I")
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	4,280,789	4,231,265
Commercial and Industrial ("C&I") | Commercial Business
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,588,228	3,569,388
Commercial and Industrial ("C&I") | Commercial Business | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	3,378,070	3,380,212
Commercial and Industrial ("C&I") | Commercial Business | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	94,628	69,687
Commercial and Industrial ("C&I") | Commercial Business | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	115,530	119,489
Commercial and Industrial ("C&I") | Trade finance
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	692,561	661,877
Commercial and Industrial ("C&I") | Trade finance | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	676,601	632,617
Commercial and Industrial ("C&I") | Trade finance | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	8,849	24,778
Commercial and Industrial ("C&I") | Trade finance | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	7,111	4,482
Consumer
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	843,794	744,882
Consumer | Student loans
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	562,819	475,799
Consumer | Student loans | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	562,752	475,799
Consumer | Student loans | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	67
Consumer | Other Consumer
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	280,975	269,083
Consumer | Other Consumer | Pass/Watch
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	274,307	261,136
Consumer | Other Consumer | Special Mention
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	1,328	1,115
Consumer | Other Consumer | Substandard
Credit quality indicator disclosures
Loans receivable, excluding covered loans, gross	$ 5,340	$ 6,832