FAIR VALUE MEASUREMENT AND FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale investment securities
Total available-for-sale investment securities	$ 2,952,277	$ 2,626,617
Derivative
Derivative assets	6,510	12,383
Derivative liabilities	(98,748)	(56,493)
U.S. Treasury securities
Available-for-sale investment securities
Total available-for-sale investment securities	752,605	873,435
U.S. government agency and U.S. government sponsored enterprise debt securities
Available-for-sale investment securities
Total available-for-sale investment securities	701,844	311,024
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Available-for-sale investment securities
Total available-for-sale investment securities	273,350	141,420
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Available-for-sale investment securities
Total available-for-sale investment securities	754,898	791,088
Municipal securities
Available-for-sale investment securities
Total available-for-sale investment securities	206,825	250,448
Other residential mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	66,537	53,918
Other commercial mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities		34,053
Corporate debt securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	141,126	115,182
Corporate debt securities | Non-investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	10,524	14,681
Other securities
Available-for-sale investment securities
Total available-for-sale investment securities	44,568	41,368
Fair Value, Measurements, Recurring
Available-for-sale investment securities
Total available-for-sale investment securities	2,952,277	2,626,617
Fair Value, Measurements, Recurring | Foreign exchange options
Derivative
Derivative assets		6,136
Fair Value, Measurements, Recurring | Interest rate swaps on certificates of deposit
Derivative
Derivative liabilities	(3,339)	(9,922)
Fair Value, Measurements, Recurring | Interest rate swaps and caps
Derivative
Derivative assets	86,954	41,534
Derivative liabilities	(87,330)	(41,779)
Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative
Derivative assets	9,745	8,118
Derivative liabilities	(12,373)	(9,163)
Fair Value, Measurements, Recurring | Embedded derivative liabilities
Derivative
Derivative liabilities		(3,392)
Fair Value, Measurements, Recurring | U.S. Treasury securities
Available-for-sale investment securities
Total available-for-sale investment securities	752,605	873,435
Fair Value, Measurements, Recurring | U.S. government agency and U.S. government sponsored enterprise debt securities
Available-for-sale investment securities
Total available-for-sale investment securities	701,844	311,024
Fair Value, Measurements, Recurring | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Available-for-sale investment securities
Total available-for-sale investment securities	273,350	141,420
Fair Value, Measurements, Recurring | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Available-for-sale investment securities
Total available-for-sale investment securities	754,898	791,088
Fair Value, Measurements, Recurring | Municipal securities
Available-for-sale investment securities
Total available-for-sale investment securities	206,825	250,448
Fair Value, Measurements, Recurring | Other residential mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	66,537	53,918
Fair Value, Measurements, Recurring | Other commercial mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	0	34,053
Fair Value, Measurements, Recurring | Corporate debt securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	141,126	115,182
Fair Value, Measurements, Recurring | Corporate debt securities | Non-investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	10,524	14,681
Fair Value, Measurements, Recurring | Other securities
Available-for-sale investment securities
Total available-for-sale investment securities	44,568	41,368
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Available-for-sale investment securities
Total available-for-sale investment securities	788,829	905,792
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. Treasury securities
Available-for-sale investment securities
Total available-for-sale investment securities	752,605	873,435
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1) | Other securities
Available-for-sale investment securities
Total available-for-sale investment securities	36,224	32,357
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Available-for-sale investment securities
Total available-for-sale investment securities	2,163,448	1,714,297
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign exchange options
Derivative
Derivative assets		6,136
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps on certificates of deposit
Derivative
Derivative liabilities	(3,339)	(9,922)
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps and caps
Derivative
Derivative assets	86,954	41,534
Derivative liabilities	(87,330)	(41,779)
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign exchange contracts
Derivative
Derivative assets	9,745	8,118
Derivative liabilities	(12,373)	(9,163)
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. government agency and U.S. government sponsored enterprise debt securities
Available-for-sale investment securities
Total available-for-sale investment securities	701,844	311,024
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Available-for-sale investment securities
Total available-for-sale investment securities	273,350	141,420
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Available-for-sale investment securities
Total available-for-sale investment securities	754,898	791,088
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Municipal securities
Available-for-sale investment securities
Total available-for-sale investment securities	206,825	250,448
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other residential mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	66,537	53,918
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other commercial mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	0	34,053
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	141,126	115,182
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Corporate debt securities | Non-investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	10,524	8,153
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Other securities
Available-for-sale investment securities
Total available-for-sale investment securities	$ 8,344	9,011
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Available-for-sale investment securities
Total available-for-sale investment securities		6,528
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Embedded derivative liabilities
Derivative
Derivative liabilities		(3,392)
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3) | Corporate debt securities | Non-investment grade
Available-for-sale investment securities
Total available-for-sale investment securities		$ 6,528