INVESTMENTS - Summary of Investment Securities by Estimated Maturity (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Held-to-Maturity Amortized Cost
Due in one year or less	$ 143
Due after one year through five years	378,248
Due after five years through ten years	333,126
Due after ten years	187,985
Total	899,502	837,272
Held-to-Maturity Market Value
Due in one year or less	145
Due after one year through five years	378,509
Due after five years through ten years	333,058
Due after ten years	190,072
Held-to-Maturity Market Value	901,784	824,985
Available-for-Sale Amortized Cost
Due in one year or less	2,224
Due after one year through five years	354,894
Due after five years through ten years	229,056
Due after ten years	326,191
Total	912,365	945,052
Available-for-Sale Market Value
Due in one year or less	2,280
Due after one year through five years	354,636
Due after five years through ten years	223,006
Due after ten years	317,793
Available-for-Sale Market Value	$ 897,715	$ 913,601