AVAILABLE-FOR-SALE INVESTMENT SECURITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities
Amortized Cost	$ 3,783,829	$ 2,619,307
Gross Unrealized Gains	11,744	21,278
Gross Unrealized Losses	(22,347)	(13,968)
Available-for-sale investment securities, at fair value	3,773,226	2,626,617
U.S. Treasury securities
Schedule of Available-for-sale Securities
Amortized Cost	1,002,874	873,101
Gross Unrealized Gains	33	1,971
Gross Unrealized Losses	(4,392)	(1,637)
Available-for-sale investment securities, at fair value	998,515	873,435
U.S. government agency and U.S. government sponsored enterprise debt securities
Schedule of Available-for-sale Securities
Amortized Cost	771,288	311,927
Gross Unrealized Gains	555	490
Gross Unrealized Losses	(2,994)	(1,393)
Available-for-sale investment securities, at fair value	768,849	311,024
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Schedule of Available-for-sale Securities
Amortized Cost	354,418	140,957
Gross Unrealized Gains	268	1,056
Gross Unrealized Losses	(3,024)	(593)
Available-for-sale investment securities, at fair value	351,662	141,420
U.S. government agency and U.S. government sponsored enterprise mortgage-backed securities - Residential mortgage-backed securities
Schedule of Available-for-sale Securities
Amortized Cost	996,255	785,412
Gross Unrealized Gains	7,542	9,754
Gross Unrealized Losses	(6,401)	(4,078)
Available-for-sale investment securities, at fair value	997,396	791,088
Municipal securities
Schedule of Available-for-sale Securities
Amortized Cost	173,785	245,408
Gross Unrealized Gains	2,657	6,202
Gross Unrealized Losses	(793)	(1,162)
Available-for-sale investment securities, at fair value	175,649	250,448
Other residential mortgage-backed securities: \| Investment grade
Schedule of Available-for-sale Securities
Amortized Cost	62,133	52,694
Gross Unrealized Gains	433	1,359
Gross Unrealized Losses	(173)	(135)
Available-for-sale investment securities, at fair value	62,393	53,918
Other commercial mortgage-backed securities: \| Investment grade
Schedule of Available-for-sale Securities
Amortized Cost		34,000
Gross Unrealized Gains		53
Gross Unrealized Losses		0
Available-for-sale investment securities, at fair value		34,053
Corporate debt securities: \| Investment grade
Schedule of Available-for-sale Securities
Amortized Cost	366,921	116,236
Gross Unrealized Gains	132	0
Gross Unrealized Losses	(2,340)	(1,054)
Available-for-sale investment securities, at fair value	364,713	115,182
Corporate debt securities: \| Non-investment grade
Schedule of Available-for-sale Securities
Amortized Cost	11,491	17,881
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,849)	(3,200)
Available-for-sale investment securities, at fair value	9,642	14,681
Other securities
Schedule of Available-for-sale Securities
Amortized Cost	44,664	41,691
Gross Unrealized Gains	124	393
Gross Unrealized Losses	(381)	(716)
Available-for-sale investment securities, at fair value	$ 44,407	$ 41,368

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section S99
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