ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		8 Months Ended	9 Months Ended	12 Months Ended
	Jan. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance				$ 5,554,059
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings		$ 1,451		(3,115)
Total other comprehensive income (loss)		(38,159)		(935,931)
Ending Balance	$ 5,554,059	4,805,236		4,805,236
Accumulated Other Comprehensive Income (Loss)
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Other comprehensive income (loss) before reclassifications				(941,559)
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings				(3,115)
Amounts reclassified from accumulated other comprehensive income (loss)				8,743
Total other comprehensive income (loss)				(935,931)
Ending Balance		(935,931)		(935,931)
Unrealized gains and losses on available-for-sale securities
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Other comprehensive income (loss) before reclassifications				(941,473)
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings				(3,115)
Amounts reclassified from accumulated other comprehensive income (loss)				8,657
Total other comprehensive income (loss)				(935,931)
Ending Balance		$ (935,931)		(935,931)
Offset of net unrealized losses in AOCI due to impact those net unrealized losses would have on certain of the Company's insurance assets and liabilities had the net unrealized losses been recognized in net income				506,900
Gains and losses on derivative instruments
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Other comprehensive income (loss) before reclassifications				(86)
Amounts reclassified from accumulated other comprehensive income (loss)				86
Predecessor
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance	4,964,884			5,433,911
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings	(243)		$ 1,044		$ 4,494
Total other comprehensive income (loss)	465,968		(94,599)		780,200
Ending Balance	5,433,911					$ 4,964,884
Predecessor | Accumulated Other Comprehensive Income (Loss)
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance	1,418,076			1,884,044	494,066	494,066
Other comprehensive income (loss) before reclassifications	469,852					959,561
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings	(243)					3,498
Amounts reclassified from accumulated other comprehensive income (loss)	(3,641)					(39,049)
Total other comprehensive income (loss)	465,968					924,010
Ending Balance	1,884,044					1,418,076	$ 494,066
Predecessor | Unrealized gains and losses on available-for-sale securities
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance	1,484,169			1,962,130	539,003	539,003
Other comprehensive income (loss) before reclassifications	482,370					986,958
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings	(243)					3,498
Amounts reclassified from accumulated other comprehensive income (loss)	(4,166)					(45,290)
Total other comprehensive income (loss)	477,961					945,166
Ending Balance	1,962,130					1,484,169	539,003
Offset of net unrealized losses in AOCI due to impact those net unrealized losses would have on certain of the Company's insurance assets and liabilities had the net unrealized losses been recognized in net income	(492,600)					(504,400)	(189,800)
Predecessor | Gains and losses on derivative instruments
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance	(82)			(50)	(1,235)	(1,235)
Other comprehensive income (loss) before reclassifications	9					(2)
Amounts reclassified from accumulated other comprehensive income (loss)	23					1,155
Total other comprehensive income (loss)	32					1,153
Ending Balance	(50)					(82)	(1,235)
Predecessor | Minimum Pension Liability Adjustment
Changes in Accumulated Other Comprehensive Income (Loss) by Component
Beginning Balance	(66,011)			$ (78,036)	(43,702)	(43,702)
Other comprehensive income (loss) before reclassifications	(12,527)					(27,395)
Amounts reclassified from accumulated other comprehensive income (loss)	502		$ 1,173		$ 3,520	5,086
Total other comprehensive income (loss)	(12,025)					(22,309)
Ending Balance	$ (78,036)					$ (66,011)	$ (43,702)