DEBT AND OTHER OBLIGATIONS - Non-Recourse Funding Obligations (Details)				3 Months Ended		12 Months Ended
	Jan. 15, 2016 USD ($)	Jan. 14, 2016 USD ($) series	Oct. 10, 2012 USD ($)	Mar. 31, 2017 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Repurchase of outstanding non-recourse funding obligations				$ 0	$ 11,300,000
Non-recourse funding obligations, outstanding principal				2,729,691,000		$ 2,740,691,000
Non-recourse funding obligations				2,785,056,000		2,796,474,000
Financing Agreement With Golden Gate And Syndicate Of Risk Takers
Debt Instrument [Line Items]
Term of financing agreement	18 years
Financing capacity under the agreement	$ 2,188,000,000.000
Golden Gate | Steel City Notes
Debt Instrument [Line Items]
Outstanding non-recourse funding obligations				$ 2,090,000,000
Stated interest rate (as a percent)				4.75%
Golden Gate | Non-recourse Funding Obligations Series
Debt Instrument [Line Items]
Outstanding non-recourse funding obligations	800,000,000	$ 800,000,000
Number of series of non-recourse funding obligations | series		3
Golden Gate | Series A1 Non-recourse Funding Obligation
Debt Instrument [Line Items]
Outstanding non-recourse funding obligations		$ 400,000,000
Stated interest rate (as a percent)		7.375%
Golden Gate | Series A2 Non-recourse Funding Obligation
Debt Instrument [Line Items]
Outstanding non-recourse funding obligations		$ 100,000,000
Stated interest rate (as a percent)		8.00%
Golden Gate | Series A3 Non-recourse Funding Obligation
Debt Instrument [Line Items]
Outstanding non-recourse funding obligations		$ 300,000,000
Stated interest rate (as a percent)		8.45%
Golden Gate | Surplus Notes | Steel City Notes
Debt Instrument [Line Items]
Initial principal amount	2,188,000,000.000
Aggregate principal balance				$ 2,090,000,000
Steel City | Surplus Notes | Golden Gate Surplus Notes
Debt Instrument [Line Items]
Initial principal amount	$ 2,188,000,000.000
Golden Gate Captive Insurance Company
Debt Instrument [Line Items]
Non-recourse funding obligations, outstanding principal				2,090,000,000		2,116,000,000
Non-recourse funding obligations				$ 2,090,000,000		$ 2,116,000,000
Non-recourse funding obligation, year-to-date weighted-average interest rate				4.75%		4.75%
Golden Gate II
Debt Instrument [Line Items]
Outstanding non-recourse funding obligations				$ 575,000,000
Non-recourse funding obligations held by external parties				58,600,000
Non-recourse funding obligations held by affiliates				516,400,000
Payments under support agreement obligation				0
Amount of support agreement obligations collateralized				2,800,000
Non-recourse funding obligations, outstanding principal				58,600,000		$ 58,600,000
Non-recourse funding obligations				$ 50,006,000		$ 49,983,000
Non-recourse funding obligation, year-to-date weighted-average interest rate				2.78%		2.52%
Golden Gate V and Red Mountain
Debt Instrument [Line Items]
Payments under support agreement obligation				$ 0
Term of transaction			20 years
Maximum financing capacity under transaction			$ 945,000,000
Red Mountain
Debt Instrument [Line Items]
Maximum financing capacity under transaction			945,000,000
Principal amount of note issued			$ 275,000,000	580,000,000
Future scheduled capital contributions				128,300,000
Golden Gate V
Debt Instrument [Line Items]
Outstanding non-recourse funding obligations				$ 580,000,000
Stated interest rate (as a percent)				6.25%
Maximum financing capacity under transaction				$ 945,000,000
Non-recourse funding obligations, outstanding principal				580,000,000		$ 565,000,000
Non-recourse funding obligations				$ 642,599,000		$ 628,025,000
Non-recourse funding obligation, year-to-date weighted-average interest rate				5.12%		5.12%
MONY
Debt Instrument [Line Items]
Non-recourse funding obligations, outstanding principal				$ 1,091,000		$ 1,091,000
Non-recourse funding obligations				$ 2,451,000		$ 2,466,000
Non-recourse funding obligation, year-to-date weighted-average interest rate				6.19%		6.19%