INVESTMENT OPERATIONS - Schedule of Amortized Cost and Fair Value of the Company's Investments Classified as Available-for-Sale (Details) - Successor - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Sep. 30, 2016	Dec. 31, 2015
Investment [Line Items]
Amortized Cost	$ 37,620,475	$ 36,612,808
Gross Unrealized Gains	649,246	53,197
Gross Unrealized Losses	(787,820)	(2,929,180)
Fair Value	37,481,901	33,736,825
Total OTTI Recognized in OCI	(909)	(605)
Residential mortgage-backed securities
Investment [Line Items]
Amortized Cost	1,842,012	1,773,099
Gross Unrealized Gains	49,259	9,286
Gross Unrealized Losses	(4,558)	(17,112)
Fair Value	1,886,713	1,765,273
Total OTTI Recognized in OCI	0	0
Commercial mortgage-backed securities
Investment [Line Items]
Amortized Cost	1,654,152	1,327,288
Gross Unrealized Gains	31,706	428
Gross Unrealized Losses	(2,632)	(41,852)
Fair Value	1,683,226	1,285,864
Total OTTI Recognized in OCI	0	0
Other asset-backed securities
Investment [Line Items]
Amortized Cost	1,202,982	813,056
Gross Unrealized Gains	14,625	2,758
Gross Unrealized Losses	(15,691)	(18,763)
Fair Value	1,201,916	797,051
Total OTTI Recognized in OCI	0	0
U.S. government-related securities
Investment [Line Items]
Amortized Cost	1,299,876	1,566,260
Gross Unrealized Gains	13,092	449
Gross Unrealized Losses	(1,789)	(34,532)
Fair Value	1,311,179	1,532,177
Total OTTI Recognized in OCI	0	0
Other government-related securities
Investment [Line Items]
Amortized Cost	18,350	18,483
Gross Unrealized Gains	184	0
Gross Unrealized Losses	(2)	(743)
Fair Value	18,532	17,740
Total OTTI Recognized in OCI	0	0
States, municipals, and political subdivisions
Investment [Line Items]
Amortized Cost	1,725,351	1,729,732
Gross Unrealized Gains	25,239	682
Gross Unrealized Losses	(23,329)	(126,814)
Fair Value	1,727,261	1,603,600
Total OTTI Recognized in OCI	0	0
Corporate securities
Investment [Line Items]
Amortized Cost	28,966,811	28,433,530
Gross Unrealized Gains	488,460	26,147
Gross Unrealized Losses	(731,249)	(2,681,020)
Fair Value	28,724,022	25,778,657
Total OTTI Recognized in OCI	(909)	(605)
Preferred Stock
Investment [Line Items]
Amortized Cost	94,362	64,362
Gross Unrealized Gains	1,227	192
Gross Unrealized Losses	(1,815)	(1,867)
Fair Value	93,774	62,687
Total OTTI Recognized in OCI	0	0
Fixed maturities
Investment [Line Items]
Amortized Cost	36,803,896	35,725,810
Gross Unrealized Gains	623,792	39,942
Gross Unrealized Losses	(781,065)	(2,922,703)
Fair Value	36,646,623	32,843,049
Total OTTI Recognized in OCI	(909)	(605)
Equity securities
Investment [Line Items]
Amortized Cost	673,709	684,888
Gross Unrealized Gains	25,454	13,255
Gross Unrealized Losses	(6,755)	(6,477)
Fair Value	692,408	691,666
Total OTTI Recognized in OCI	0	0
Short-term investments
Investment [Line Items]
Amortized Cost	142,870	202,110
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	142,870	202,110
Total OTTI Recognized in OCI	$ 0	$ 0

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount before tax of other than temporary impairment (OTTI) on investment in available-for-sale debt security, recognized in other comprehensive loss.

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