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INVESTMENT OPERATIONS - Additional Information (Details)	1 Months Ended	3 Months Ended		5 Months Ended	6 Months Ended	11 Months Ended
	Jan. 31, 2015 USD ($)	Jun. 30, 2016 USD ($) subsidiary position	Jun. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2016 USD ($) subsidiary position	Dec. 31, 2015 USD ($) subsidiary
Successor
Investment [Line Items]
Other-than-temporary impairments of investments recorded		$ 5,527,000	$ 13,395,000	$ 13,395,000	$ 8,296,000
Other-than-temporary impairments of investments recorded in other comprehensive income (loss)		4,560,000	7,661,000	7,661,000	4,712,000
Gross unrealized loss greater than twelve months		$ 994,638,000			$ 994,638,000	$ 0
Total positions that were in an unrealized loss position \| position		1,414			1,414
Available-for-sale securities, fair value		$ 37,042,090,000			$ 37,042,090,000	33,847,196,000
Available-for-sale securities, amortized cost		37,625,082,000			37,625,082,000	36,724,217,000
Other-than-temporary impairments on held-to-maturity securities		0	0	0	0
Held-to-maturity securities, unrecognized holding losses						78,300,000
Predecessor
Investment [Line Items]
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 \| Successor
Investment [Line Items]
Trading securities		2,800,000,000			2,800,000,000	2,700,000,000
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	$ 0	0
Available-for-sale securities, fair value		36,062,434,000			36,062,434,000	32,909,201,000
Available-for-sale securities, amortized cost		36,666,726,000			36,666,726,000	35,793,000,000
Gross unrealized gains		97,387,000			97,387,000	0
Gross unrealized losses		22,879,000			22,879,000	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
Equity securities \| Successor
Investment [Line Items]
Trading securities		8,000,000			8,000,000	8,300,000
Gross unrealized loss greater than twelve months		3,867,000			3,867,000	0
Available-for-sale securities, fair value		731,661,000			731,661,000	731,004,000
Available-for-sale securities, amortized cost		710,361,000			710,361,000	724,226,000
Short-term investments \| Successor
Investment [Line Items]
Trading securities		38,200,000			38,200,000	61,700,000
Available-for-sale securities, fair value		247,995,000			247,995,000	206,991,000
Available-for-sale securities, amortized cost		247,995,000			247,995,000	206,991,000
Residential mortgage-backed securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months		6,150,000			6,150,000	0
Available-for-sale securities, fair value		1,941,684,000			1,941,684,000	1,765,273,000
Available-for-sale securities, amortized cost		1,900,934,000			1,900,934,000	1,773,099,000
Commercial mortgage-backed securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months		3,443,000			3,443,000	0
Available-for-sale securities, fair value		1,596,760,000			1,596,760,000	1,286,887,000
Available-for-sale securities, amortized cost		1,570,208,000			1,570,208,000	1,328,317,000
Other asset-backed securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months		34,867,000			$ 34,867,000	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		1,120,642,000			$ 1,120,642,000	797,051,000
Available-for-sale securities, amortized cost		1,151,430,000			1,151,430,000	813,056,000
U.S. government related \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months		200,000			200,000
States, municipals, and political subdivisions \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months		21,320,000			21,320,000	0
Available-for-sale securities, fair value		1,737,499,000			1,737,499,000	1,603,600,000
Available-for-sale securities, amortized cost		1,727,664,000			1,727,664,000	1,729,732,000
Corporate securities \| Successor
Investment [Line Items]
Gross unrealized loss greater than twelve months		923,124,000			923,124,000	0
Available-for-sale securities, fair value		28,210,946,000			28,210,946,000	25,843,786,000
Available-for-sale securities, amortized cost		28,883,011,000			28,883,011,000	$ 28,499,691,000
Below investment grade \| Successor
Investment [Line Items]
Trading securities		270,800,000			270,800,000
Available-for-sale securities, fair value		1,800,000,000			1,800,000,000
Available-for-sale securities, amortized cost		1,900,000,000			1,900,000,000
Securities not publicly traded		325,500,000			$ 325,500,000
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			$ 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			$ 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			2