INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	$ 669,093	$ 770,755
Held To Maturity Gross Unrealized Gain Accumulated In Investments	925	9,021
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	8,333	1,302
Held-to-Maturity Market Value	661,685	778,474
Available-for-Sale Amortized Cost	875,928	1,017,104
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	6,250	16,725
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	27,431	1,733
Available-for-Sale Market Value	854,747	1,032,096
U.S. Treasuries
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	0
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	0
Held-to-Maturity Market Value	0
Available-for-Sale Amortized Cost	97
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	4
Available-for-Sale Market Value	93
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	19,462	20,512
Held To Maturity Gross Unrealized Gain Accumulated In Investments	0	679
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	864	0
Held-to-Maturity Market Value	18,598	21,191
Available-for-Sale Amortized Cost	10,266	15,562
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	333
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	142	0
Available-for-Sale Market Value	10,124	15,895
Mortgage-backed securities
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	637,170	740,891
Held To Maturity Gross Unrealized Gain Accumulated In Investments	768	8,077
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	6,561	1,290
Held-to-Maturity Market Value	631,377	747,678
Available-for-Sale Amortized Cost	652,808	854,150
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	6,093	14,564
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	20,818	1,485
Available-for-Sale Market Value	638,083	867,229
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Held-to-Maturity Amortized Cost	12,461	9,352
Held To Maturity Gross Unrealized Gain Accumulated In Investments	157	265
Held To Maturity Securities Gross Unrealized Loss Accumulated In Investments	908	12
Held-to-Maturity Market Value	11,710	9,605
Available-for-Sale Amortized Cost	34,005	35,913
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	31	169
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	2,294	84
Available-for-Sale Market Value	31,742	35,998
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	67,816	57,000
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	90
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	359	1
Available-for-Sale Market Value	67,457	57,089
Other securities
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	110,936	54,479
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	126	1,569
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	3,814	163
Available-for-Sale Market Value	$ 107,248	$ 55,885