FAIR VALUE MEASUREMENT AND FAIR VALUE OF FINANCIAL INSTRUMENTS (Details 8) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Financial Assets:
Cash and cash equivalents	$ 1,875,703	$ 1,039,885	$ 1,115,753	$ 895,820
Short-term investments	258,028	338,714
Securities purchased under resale agreements (“resale agreements”)	1,400,000	1,225,000
Loans held for sale	349,375	45,950
Loans receivable, net	22,381,302	21,468,270
Investment in Federal Home Loan Bank (“FHLB”) stock	18,156	31,239
Investment in Federal Reserve Bank stock	54,786	54,451
Customer deposit accounts:
Short-term borrowings	3,146	0
FHLB advances	318,872	317,241
Securities sold under repurchase agreements (“repurchase agreements”)	150,000	795,000
Long-term debt	211,024	225,848
Carrying Amount
Financial Assets:
Cash and cash equivalents	1,875,703	1,039,885
Short-term investments	258,028	338,714
Securities purchased under resale agreements (“resale agreements”)	1,400,000	1,225,000
Loans held for sale	349,375	45,950
Loans receivable, net	22,381,302	21,468,270
Investment in Federal Home Loan Bank (“FHLB”) stock	18,156	31,239
Investment in Federal Reserve Bank stock	54,786	54,451
Accrued interest receivable	85,388	88,303
Customer deposit accounts:
Demand, savings and money market deposits	20,105,272	17,896,035
Time deposits	6,653,778	6,112,739
Short-term borrowings	3,146
FHLB advances	318,872	317,241
Securities sold under repurchase agreements (“repurchase agreements”)	150,000	795,000
Accrued interest payable	9,403	11,303
Long-term debt	211,024	225,848
Fair Value Measurements
Financial Assets:
Cash and cash equivalents	1,875,703	1,039,885
Short-term investments	258,028	338,714
Securities purchased under resale agreements (“resale agreements”)	1,398,488	1,191,060
Loans held for sale	353,095	45,950
Loans receivable, net	21,947,953	20,997,379
Investment in Federal Home Loan Bank (“FHLB”) stock	18,156	31,239
Investment in Federal Reserve Bank stock	54,786	54,451
Accrued interest receivable	85,388	88,303
Customer deposit accounts:
Demand, savings and money market deposits	20,105,272	17,896,035
Time deposits	6,640,017	6,095,217
Short-term borrowings	3,146
FHLB advances	332,478	336,302
Securities sold under repurchase agreements (“repurchase agreements”)	209,930	870,434
Accrued interest payable	9,403	11,303
Long-term debt	187,630	205,777
Fair Value Measurements | Quoted Prices in Active Markets for Identical Assets (Level 1)
Financial Assets:
Cash and cash equivalents	1,875,703	1,039,885
Fair Value Measurements | Significant Other Observable Inputs (Level 2)
Financial Assets:
Short-term investments	258,028	338,714
Securities purchased under resale agreements (“resale agreements”)	1,398,488	1,191,060
Loans held for sale	353,095	45,950
Investment in Federal Home Loan Bank (“FHLB”) stock	18,156	31,239
Investment in Federal Reserve Bank stock	54,786	54,451
Accrued interest receivable	85,388	88,303
Customer deposit accounts:
Demand, savings and money market deposits	20,105,272	17,896,035
Time deposits	6,640,017	6,095,217
Short-term borrowings	3,146
FHLB advances	332,478	336,302
Securities sold under repurchase agreements (“repurchase agreements”)	209,930	870,434
Accrued interest payable	9,403	11,303
Long-term debt	187,630	205,777
Fair Value Measurements | Significant Unobservable Inputs (Level 3)
Financial Assets:
Loans receivable, net	$ 21,947,953	$ 20,997,379