INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Investment Holdings [Line Items]
Total	$ 839,666us-gaap_HeldToMaturitySecurities	$ 867,996us-gaap_HeldToMaturitySecurities
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	16,149	9,112
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(732)	(2,359)
Held-to-Maturity Market Value	855,083	874,749
Total	893,123	849,504
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	9,736	6,760
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(10,690)	(15,796)
Investment securities available-for-sale	892,169us-gaap_AvailableForSaleSecurities	840,468us-gaap_AvailableForSaleSecurities
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	97	97
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	2	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	0	0
Investment securities available-for-sale	99	97
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Total	17,041	17,570
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	209	24
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	(23)
Held-to-Maturity Market Value	17,250	17,571
Total	11,318	11,814
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	186	67
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	0	(1)
Investment securities available-for-sale	11,504	11,880
Mortgage-backed securities
Investment Holdings [Line Items]
Total	774,331	801,465
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	14,934	7,813
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(482)	(2,064)
Held-to-Maturity Market Value	788,783	807,214
Total	588,766	611,497
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	5,419	4,462
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(8,615)	(13,211)
Investment securities available-for-sale	585,570	602,748
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	43,495	44,164
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	955	1,275
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(250)	(193)
Held-to-Maturity Market Value	44,200	45,246
Total	85,401	73,649
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	2,376	883
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,018)	(947)
Investment securities available-for-sale	86,759	73,585
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	125,338	74,784
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	304	155
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(181)	(103)
Investment securities available-for-sale	125,461	74,836
Other securities
Investment Holdings [Line Items]
Total	4,799	4,797
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	51	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	0	(79)
Held-to-Maturity Market Value	4,850	4,718
Total	82,203	77,663
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,449	1,193
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(876)	(1,534)
Investment securities available-for-sale	$ 82,776	$ 77,322

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

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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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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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