ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Changes in Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Jan. 31, 2015	Dec. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Successor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		$ 0	$ (1,241,134)
Other comprehensive income (loss) before reclassifications		(1,258,189)	602,014
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings		(393)	(6,782)
Amounts reclassified from accumulated other comprehensive income (loss)		17,448	(8,621)
Total other comprehensive income (loss)		(1,241,134)	586,611
Ending Balance	$ 0	(1,241,134)	(654,523)	$ (1,241,134)
Predecessor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	1,418,076	1,884,044		1,418,076	$ 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
Unrealized gains and losses on available-for-sale securities | Successor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		0	(1,247,065)
Other comprehensive income (loss) before reclassifications		(1,264,034)	606,985
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings		(393)	(6,782)
Amounts reclassified from accumulated other comprehensive income (loss)		17,362	(9,460)
Total other comprehensive income (loss)		(1,247,065)	590,743
Ending Balance	0	(1,247,065)	(656,322)	(1,247,065)
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			424,100	623,000
Unrealized gains and losses on available-for-sale securities | Predecessor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	1,484,169	1,962,130		1,484,169	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)	623,000			(504,400)	(189,800)
Accumulated Gain and Loss Derivatives | Successor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		0	0
Other comprehensive income (loss) before reclassifications		(86)	688
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings		0	0
Amounts reclassified from accumulated other comprehensive income (loss)		86	39
Total other comprehensive income (loss)		0	727
Ending Balance	0	0	727	0
Accumulated Gain and Loss Derivatives | Predecessor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(82)	(50)		(82)	(1,235)
Other comprehensive income (loss) before reclassifications	9				(2)
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings	0				0
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)
Minimum Pension Benefits Liability Adjustment | Successor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		0	5,931
Other comprehensive income (loss) before reclassifications		5,931	(5,659)
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings		0	0
Amounts reclassified from accumulated other comprehensive income (loss)		0	800
Total other comprehensive income (loss)		5,931	(4,859)
Ending Balance	0	5,931	$ 1,072	5,931
Minimum Pension Benefits Liability Adjustment | Predecessor
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(66,011)	$ (78,036)		$ (66,011)	(43,702)
Other comprehensive income (loss) before reclassifications	(12,527)				(27,395)
Other comprehensive income (loss) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings	0				0
Amounts reclassified from accumulated other comprehensive income (loss)	502				5,086
Total other comprehensive income (loss)	(12,025)				(22,309)
Ending Balance	$ (78,036)				$ (66,011)	$ (43,702)