FAIR VALUE MEASUREMENT AND FAIR VALUE OF FINANCIAL INSTRUMENTS (Details) - USD ($) $ in Thousands		Jun. 30, 2015	Dec. 31, 2014
Available-for-sale investment securities
Total available-for-sale investment securities		$ 2,982,146	$ 2,626,365
Derivative
Derivative assets		10,752	12,383
Derivative liabilities		(54,746)	(56,493)
U.S. Treasury securities
Available-for-sale investment securities
Total available-for-sale investment securities		1,200,111	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		424,863	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		187,388	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		688,712	791,088
Municipal securities
Available-for-sale investment securities
Total available-for-sale investment securities		206,422	250,448
Other residential mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	[1]	61,908	53,918
Other commercial mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	[1]		34,053
Corporate debt securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	[1]	156,978	115,182
Corporate debt securities | Non-investment grade
Available-for-sale investment securities
Total available-for-sale investment securities	[1]	10,025	14,681
Other securities
Available-for-sale investment securities
Total available-for-sale investment securities		45,739	41,116
Fair Value, Measurements, Recurring
Available-for-sale investment securities
Total available-for-sale investment securities		2,982,146	2,626,365
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		(8,177)	(9,922)
Fair Value, Measurements, Recurring | Interest rate swaps and caps
Derivative
Derivative assets		44,424	41,534
Derivative liabilities		(43,810)	(41,779)
Fair Value, Measurements, Recurring | Foreign exchange contracts
Derivative
Derivative assets		11,044	8,118
Derivative liabilities		(10,186)	(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		1,200,111	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		424,863	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		187,388	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		688,712	791,088
Fair Value, Measurements, Recurring | Municipal securities
Available-for-sale investment securities
Total available-for-sale investment securities		206,422	250,448
Fair Value, Measurements, Recurring | Other residential mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities		61,908	53,918
Fair Value, Measurements, Recurring | Other commercial mortgage-backed securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities			34,053
Fair Value, Measurements, Recurring | Corporate debt securities | Investment grade
Available-for-sale investment securities
Total available-for-sale investment securities		156,978	115,182
Fair Value, Measurements, Recurring | Corporate debt securities | Non-investment grade
Available-for-sale investment securities
Total available-for-sale investment securities		10,025	14,681
Fair Value, Measurements, Recurring | Other securities
Available-for-sale investment securities
Total available-for-sale investment securities		45,739	41,116
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		1,235,645	905,540
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		1,200,111	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		35,534	32,105
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Available-for-sale investment securities
Total available-for-sale investment securities		1,746,501	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		(8,177)	(9,922)
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Interest rate swaps and caps
Derivative
Derivative assets		44,424	41,534
Derivative liabilities		(43,810)	(41,779)
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2) | Foreign exchange contracts
Derivative
Derivative assets		11,044	8,118
Derivative liabilities		(10,186)	(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		424,863	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		187,388	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		688,712	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		206,422	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		61,908	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			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		156,978	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		10,025	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		$ 10,205	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

[1] Available-for-sale investment securities rated BBB- or higher by S&P or Baa3 or higher by Moody's are considered investment grade. Conversely, available-for-sale investment securities rated lower than BBB- by S&P or lower than Baa3 by Moody's are considered non-investment grade.