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INVESTMENT OPERATIONS - Additional Information (Details)	1 Months Ended	2 Months Ended	3 Months Ended	11 Months Ended
	Jan. 31, 2015 USD ($)	Mar. 31, 2015 USD ($)	Mar. 31, 2016 USD ($) position subsidiary	Dec. 31, 2015 USD ($) subsidiary
Successor
Investment [Line Items]
Gross realized gains on investments available-for-sale (fixed maturities, equity securities, and short-term investments)		$ 1,500,000	$ 9,000,000
Gross realized losses		1,100,000	3,500,000
Impairment losses on investments available-for-sale			2,600,000
Fair value (proceeds) of securities in an unrealized gain position sold		282,900,000	309,200,000
Gain realized on the sale of securities in an unrealized gain position		1,500,000	9,000,000
Fair value (proceeds) of securities in an unrealized loss position sold		20,700,000	53,700,000
Loss realized on the sale of securities in an unrealized loss position		1,100,000	3,500,000
Other-than-temporary impairments of investments recorded		0	2,769,000
Other-than-temporary impairments of investments recorded in other comprehensive income (loss)		0	152,000
Gross unrealized loss greater than twelve months			$ 1,093,527,000	$ 0
Total positions that were in an unrealized loss position \| position			2,108
Available-for-sale securities, fair value			$ 35,525,919,000	33,847,196,000
Available-for-sale securities, amortized cost			37,429,686,000	36,724,217,000
Other-than-temporary impairments on held-to-maturity securities		0	0
Held-to-maturity securities, unrecognized holding losses				78,300,000
Predecessor
Investment [Line Items]
Gross realized gains on investments available-for-sale (fixed maturities, equity securities, and short-term investments)	$ 6,900,000
Gross realized losses	500,000
Impairment losses on investments available-for-sale	400,000
Fair value (proceeds) of securities in an unrealized gain position sold	172,600,000
Gain realized on the sale of securities in an unrealized gain position	6,900,000
Fair value (proceeds) of securities in an unrealized loss position sold	400,000
Other-than-temporary impairments of investments recorded	636,000
Other-than-temporary impairments of investments recorded in other comprehensive income (loss)	155,000
Other-than-temporary impairments on held-to-maturity securities	0
Fixed maturities
Investment [Line Items]
Other-than-temporary impairments related to fixed maturities or equity securities that the Company intended to sell or expected to be required to sell		$ 0	0
Fixed maturities \| Successor
Investment [Line Items]
Trading securities			2,700,000,000	2,700,000,000
Available-for-sale securities, fair value			34,404,351,000	32,909,201,000
Available-for-sale securities, amortized cost			36,314,789,000	35,793,000,000
Held-to-maturity securities, gross unrecognized holding losses			64,382,000	78,314,000
Fixed maturities \| Predecessor
Investment [Line Items]
Other-than-temporary impairments related to fixed maturities or equity securities that the Company intended to sell or expected to be required to sell	0
Fixed income securities \| Predecessor
Investment [Line Items]
Other-than-temporary impairments of investments recorded	$ 600,000
Equity securities \| Successor
Investment [Line Items]
Trading securities			6,800,000	8,300,000
Gross unrealized loss greater than twelve months			688,000	0
Available-for-sale securities, fair value			715,338,000	731,004,000
Available-for-sale securities, amortized cost			708,667,000	724,226,000
Short-term investments \| Successor
Investment [Line Items]
Trading securities			43,000,000	61,700,000
Available-for-sale securities, fair value			406,230,000	206,991,000
Available-for-sale securities, amortized cost			406,230,000	206,991,000
Residential mortgage-backed securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months			3,666,000	0
Available-for-sale securities, fair value			1,870,877,000	1,765,273,000
Available-for-sale securities, amortized cost			1,849,678,000	1,773,099,000
Commercial mortgage-backed securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months			5,095,000	0
Available-for-sale securities, fair value			1,462,697,000	1,286,887,000
Available-for-sale securities, amortized cost			1,465,623,000	1,328,317,000
Other asset-backed securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months			$ 6,988,000	0
Percentage of underlying collateral of student-loan backed auction rate securities guaranteed by the Federal Family Education Loan Program (FFELP), minimum			97.00%
Available-for-sale securities, fair value			$ 963,538,000	797,051,000
Available-for-sale securities, amortized cost			992,128,000	813,056,000
States, municipals, and political subdivisions \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months			44,014,000	0
Available-for-sale securities, fair value			1,661,560,000	1,603,600,000
Available-for-sale securities, amortized cost			1,729,964,000	1,729,732,000
Corporate securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months			1,029,477,000	0
Available-for-sale securities, fair value			26,925,200,000	25,843,786,000
Available-for-sale securities, amortized cost			28,760,422,000	$ 28,499,691,000
Below investment grade \| Successor
Investment [Line Items]
Trading securities			282,700,000
Available-for-sale securities, fair value			1,800,000,000
Available-for-sale securities, amortized cost			2,000,000,000
Securities not publicly traded			$ 297,600,000
Red Mountain
Investment [Line Items]
Number of wholly owned subsidiaries that were determined to be VIEs \| subsidiary				1
Ownership through an affiliate (as a percent)			100.00%
Risk of loss related to the VIE limited to the entity's investment			$ 10,000
Red Mountain \| Successor
Investment [Line Items]
Payments made			$ 0
Steel City
Investment [Line Items]
Ownership through an affiliate (as a percent)			100.00%
Risk of loss related to the VIE limited to the entity's investment			$ 10,000
Steel City \| Successor
Investment [Line Items]
Payments made			$ 0
Red Mountain and Steel City
Investment [Line Items]
Number of wholly owned subsidiaries that were determined to be VIEs \| subsidiary			2