INVESTMENTS - Summary of Investment Securities by Estimated Maturity (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Held-to-Maturity Amortized Cost
Due in one year or less	$ 268
Due after one year through five years	402,027
Due after five years through ten years	354,896
Due after ten years	143,330
Total	900,521	837,272
Held-to-Maturity Market Value
Due in one year or less	271
Due after one year through five years	401,829
Due after five years through ten years	355,179
Due after ten years	144,380
Held-to-Maturity Market Value	901,659	824,985
Available-for-Sale Amortized Cost
Due in one year or less	12,735
Due after one year through five years	348,661
Due after five years through ten years	266,513
Due after ten years	316,308
Total	944,217	945,052
Available-for-Sale Market Value
Due in one year or less	12,738
Due after one year through five years	346,665
Due after five years through ten years	260,869
Due after ten years	309,322
Available-for-Sale Market Value	$ 929,594	$ 913,601