INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	$ 899,502	$ 837,272
Held To Maturity Gross Unrealized Gain Accumulated In Investments	7,838	1,772
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	(5,556)	(14,059)
Held-to-Maturity Market Value	901,784	824,985
Available-for-Sale Amortized Cost	912,365	945,052
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	7,082	5,645
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(21,732)	(37,096)
Available-for-Sale Market Value	897,715	913,601
U.S. Treasuries
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	0	0
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	0	0
Held-to-Maturity Market Value	0	0
Available-for-Sale Amortized Cost	97	97
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(2)	(7)
Available-for-Sale Market Value	95	90
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	18,308	18,981
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	(262)	(791)
Held-to-Maturity Market Value	18,046	18,190
Available-for-Sale Amortized Cost	9,615	9,980
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(59)	(404)
Available-for-Sale Market Value	9,556	9,576
Mortgage-backed securities
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	832,159	775,025
Held To Maturity Gross Unrealized Gain Accumulated In Investments	6,772	1,337
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	(4,561)	(12,229)
Held-to-Maturity Market Value	834,370	764,133
Available-for-Sale Amortized Cost	711,113	678,267
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	5,574	5,372
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(18,641)	(28,593)
Available-for-Sale Market Value	698,046	655,046
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	25,138	25,788
Held To Maturity Gross Unrealized Gain Accumulated In Investments	210	152
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	(724)	(1,039)
Held-to-Maturity Market Value	24,624	24,901
Available-for-Sale Amortized Cost	30,469	33,410
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	41	10
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,325)	(3,097)
Available-for-Sale Market Value	29,185	30,323
Asset-backed Securities [Member]
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	0	0
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	0	0
Held-to-Maturity Market Value	0	0
Available-for-Sale Amortized Cost	57,881	114,209
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	122	1
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(6)	(616)
Available-for-Sale Market Value	57,997	113,594
Other securities
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	23,897	17,478
Held To Maturity Gross Unrealized Gain Accumulated In Investments	856	283
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	(9)	0
Held-to-Maturity Market Value	24,744	17,761
Available-for-Sale Amortized Cost	103,190	109,089
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	1,345	262
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(1,699)	(4,379)
Available-for-Sale Market Value	$ 102,836	$ 104,972