INVESTMENTS (Details 4) - 10K (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Assets measured at Fair Value
Available-for-sale securities	$ 1,905,729	$ 1,858,706
Transfers in (out of) level 1	0	0
Transfers in (out of) level 2	0	0
U.S. Agency
Assets measured at Fair Value
Available-for-sale securities	6,747	10,298
Non-U.S. govt. & agency
Assets measured at Fair Value
Available-for-sale securities	10,665	13,678
U.S. government
Assets measured at Fair Value
Available-for-sale securities	33,788	17,303
Municipal
Assets measured at Fair Value
Available-for-sale securities	481,425	522,010
Equity securities
Assets measured at Fair Value
Available-for-sale securities	410,642	418,654
Fair value measured on recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets measured at Fair Value
Available-for-sale securities	410,642	418,654
Fair value measured on recurring basis | Quoted Prices in Active Markets for Identical Assets (Level 1) | Equity securities
Assets measured at Fair Value
Available-for-sale securities	410,642	418,654
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2)
Assets measured at Fair Value
Available-for-sale securities	1,495,087	1,440,052
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2) | U.S. Agency
Assets measured at Fair Value
Available-for-sale securities	6,747	10,298
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2) | Corporate Bond Securities [Member]
Assets measured at Fair Value
Available-for-sale securities	562,690	526,038
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2) | Mortgage-backed
Assets measured at Fair Value
Available-for-sale securities	264,468	244,416
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2) | ABS/CMBS
Assets measured at Fair Value
Available-for-sale securities	135,304	106,309
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2) | Non-U.S. govt. & agency
Assets measured at Fair Value
Available-for-sale securities	10,665	13,678
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2) | U.S. government
Assets measured at Fair Value
Available-for-sale securities	33,788	17,303
Fair value measured on recurring basis | Significant Other Observable Inputs (Level 2) | Municipal
Assets measured at Fair Value
Available-for-sale securities	481,425	522,010
Fair value measured on recurring basis | Total
Assets measured at Fair Value
Available-for-sale securities	1,905,729	1,858,706
Fair value measured on recurring basis | Total | U.S. Agency
Assets measured at Fair Value
Available-for-sale securities	6,747	10,298
Fair value measured on recurring basis | Total | Corporate Bond Securities [Member]
Assets measured at Fair Value
Available-for-sale securities	562,690	526,038
Fair value measured on recurring basis | Total | Mortgage-backed
Assets measured at Fair Value
Available-for-sale securities	264,468	244,416
Fair value measured on recurring basis | Total | ABS/CMBS
Assets measured at Fair Value
Available-for-sale securities	135,304	106,309
Fair value measured on recurring basis | Total | Non-U.S. govt. & agency
Assets measured at Fair Value
Available-for-sale securities	10,665	13,678
Fair value measured on recurring basis | Total | U.S. government
Assets measured at Fair Value
Available-for-sale securities	33,788	17,303
Fair value measured on recurring basis | Total | Municipal
Assets measured at Fair Value
Available-for-sale securities	481,425	522,010
Fair value measured on recurring basis | Total | Equity securities
Assets measured at Fair Value
Available-for-sale securities	$ 410,642	$ 418,654