INVESTMENT SECURITIES (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 11,786,164	$ 11,970,063
Gross Unrealized Gains	107,879	67,095
Gross Unrealized Loss	(219,001)	(390,918)
Fair Value	11,675,042	11,646,240
US Treasury and government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,000	24,993
Gross Unrealized Gains	0	4
Gross Unrealized Loss	0	0
Fair Value	8,000	24,997
Corporate debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,191,038	2,195,004
Gross Unrealized Gains	46,151	35,611
Gross Unrealized Loss	(2,840)	(12,435)
Fair Value	2,234,349	2,218,180
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,584,562	2,727,235
Gross Unrealized Gains	23,251	9,345
Gross Unrealized Loss	(3,152)	(4,350)
Fair Value	2,604,661	2,732,230
Equity securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,473	10,331
Gross Unrealized Gains	2	0
Gross Unrealized Loss	(312)	(490)
Fair Value	10,163	9,841
State and municipal securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,807,170	1,891,996
Gross Unrealized Gains	36,355	20,515
Gross Unrealized Loss	(13,249)	(62,362)
Fair Value	1,830,276	1,850,149
Mortgage-backed securities, U.S. government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,910,373	1,904,178
Gross Unrealized Gains	511	134
Gross Unrealized Loss	(44,925)	(103,889)
Fair Value	1,865,959	1,800,423
Mortgage-backed securities, FHLMC and FNMA debt securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,260,969	3,202,428
Gross Unrealized Gains	1,356	1,486
Gross Unrealized Loss	(154,523)	(207,392)
Fair Value	3,107,802	2,996,522
Mortgage-backed securities, Non-agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,579	13,898
Gross Unrealized Gains	253	0
Gross Unrealized Loss	0	0
Fair Value	$ 13,832	$ 13,898