ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)
Benefits and settlement expenses, net of reinsurance ceded									$ (2,786,463)	$ (2,473,988)	$ (2,317,121)
Realized investment gains (losses): All other investments									205,302	(121,537)	232,836
Net impairment losses recognized in earnings									(7,275)	(22,447)	(58,144)
Income before income tax	230,443	184,120	172,615	151,611	120,403	113,355	78,927	109,814	738,789	422,499	459,579
Tax (expense) or benefit	(78,917)	(62,287)	(56,572)	(49,062)	(31,931)	(37,107)	(25,923)	(35,936)	(246,838)	(130,897)	(151,043)
Gains and losses on derivative instruments | Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)
Benefits and settlement expenses, net of reinsurance ceded									(1,777)	(2,349)
Income before income tax									(1,777)	(2,349)
Tax (expense) or benefit									622	822
Net of tax									(1,155)	(1,527)
Unrealized gains and losses on available-for-sale securities | Amount Reclassified from Accumulated Other Comprehensive Income (Loss)
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)
Realized investment gains (losses): All other investments									75,569	66,437
Net impairment losses recognized in earnings									(7,275)	(22,447)
Income before income tax									68,294	43,990
Tax (expense) or benefit									(23,903)	(15,396)
Net of tax									$ 44,391	$ 28,594