INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Investment Holdings [Line Items]
Total	$ 628,497	$ 726,259
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	17,591	7,911
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(337)	(2,219)
Held-to-Maturity Market Value	645,751	731,951
Total	1,110,784	1,203,065
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	14,961	6,078
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(5,251)	(18,501)
Investment securities available-for-sale	1,120,494	1,190,642
U.S. Treasuries
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	98	98
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	4	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	0	(1)
Investment securities available-for-sale	102	97
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Total	13,811	15,486
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	389	121
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	14,200	15,607
Total	7,471	8,183
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	226	157
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Investment securities available-for-sale	7,697	8,340
Mortgage-backed securities
Investment Holdings [Line Items]
Total	591,224	678,318
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	16,639	7,452
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(337)	(1,999)
Held-to-Maturity Market Value	607,526	683,771
Total	662,535	775,285
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	8,714	2,708
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(2,241)	(12,926)
Investment securities available-for-sale	669,008	765,067
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	23,462	27,646
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	563	338
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	(99)
Held-to-Maturity Market Value	24,025	27,885
Total	119,168	105,212
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	3,574	2,655
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(502)	(730)
Investment securities available-for-sale	122,240	107,137
Asset-backed Securities [Member]
Investment Holdings [Line Items]
Total	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	0
Held-to-Maturity Market Value	0	0
Total	286,427	236,411
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,508	35
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,944)	(3,445)
Investment securities available-for-sale	285,991	233,001
Other securities
Investment Holdings [Line Items]
Total	0	4,809
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	(121)
Held-to-Maturity Market Value	0	4,688
Total	35,085	77,876
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	935	523
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(564)	(1,399)
Investment securities available-for-sale	$ 35,456	$ 77,000

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

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