INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Investment Holdings [Line Items]
Total	$ 900,521	$ 837,272
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	6,502	1,772
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(5,364)	(14,059)
Held-to-Maturity Market Value	901,659	824,985
Total	944,217	945,052
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	7,378	5,645
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(22,001)	(37,096)
Investment securities available-for-sale	929,594	913,601
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	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(3)	(7)
Investment securities available-for-sale	94	90
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Total	17,917	18,981
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	0	0
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(231)	(791)
Held-to-Maturity Market Value	17,686	18,190
Total	12,304	9,980
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	3	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(37)	(404)
Investment securities available-for-sale	12,270	9,576
Mortgage-backed securities
Investment Holdings [Line Items]
Total	832,728	775,025
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	5,290	1,337
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(4,656)	(12,229)
Held-to-Maturity Market Value	833,362	764,133
Total	700,167	678,267
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	4,967	5,372
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(19,273)	(28,593)
Investment securities available-for-sale	685,861	655,046
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	26,308	25,788
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	442	152
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(418)	(1,039)
Held-to-Maturity Market Value	26,332	24,901
Total	49,824	33,410
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	588	10
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,008)	(3,097)
Investment securities available-for-sale	49,404	30,323
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	76,693	114,209
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	244	1
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1)	(616)
Investment securities available-for-sale	76,936	113,594
Other securities
Investment Holdings [Line Items]
Total	23,568	17,478
Held-to-maturity Securities, Accumulated Unrecognized Holding Gain	770	283
Held-to-maturity Securities, Accumulated Unrecognized Holding Loss	(59)	0
Held-to-Maturity Market Value	24,279	17,761
Total	105,132	109,089
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,576	262
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,679)	(4,379)
Investment securities available-for-sale	$ 105,029	$ 104,972