INVESTMENTS (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Amortized cost of available-for-sale debt securities by contractual maturity
Due in one year or less	$ 25,339
Due after one year through five years	140,966
Due after five years through 10 years	680,044
Due after 10 years	157,058
Total amortized cost	1,339,224
Fair value of available-for-sale debt securities by contractual maturity
Due in one year or less	25,448
Due after one year through five years	150,519
Due after five years through 10 years	722,419
Due after 10 years	162,635
Total fair value	1,413,570	1,378,582
Amortized cost of debt securities held-to-maturity by contractual maturity
Due after one year through five years	651
Due after 10 years	5,085
Total amortized cost	5,736
Fair value of debt securities held-to-maturity by contractual maturity
Due after one year through five years	711
Due after 10 years	5,095
Total fair value	5,806
Mtge/ABS/CMO
Amortized cost of available-for-sale debt securities by contractual maturity
Total amortized cost	335,817
Fair value of available-for-sale debt securities by contractual maturity
Total fair value	$ 352,549