DEBT AND OTHER OBLIGATIONS - Non-Recourse Funding Obligations (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Outstanding Principal	$ 2,905,940	$ 2,944,940
Carrying Value	2,913,621	2,952,822
Golden Gate Captive Insurance Company
Debt Instrument [Line Items]
Outstanding Principal	1,950,000	2,014,000
Carrying Value	$ 1,950,000	$ 2,014,000
Year-to-Date Weighted-Avg Interest Rate	4.75%	4.75%
Golden Gate II Captive Insurance Company
Debt Instrument [Line Items]
Outstanding Principal	$ 309,849	$ 309,849
Carrying Value	$ 255,867	$ 255,132
Year-to-Date Weighted-Avg Interest Rate	3.94%	3.11%
Golden Gate V Vermont Captive Insurance Company
Debt Instrument [Line Items]
Outstanding Principal	$ 645,000	$ 620,000
Carrying Value	$ 705,381	$ 681,285
Year-to-Date Weighted-Avg Interest Rate	5.12%	5.12%
MONY Life Insurance Company
Debt Instrument [Line Items]
Outstanding Principal	$ 1,091	$ 1,091
Carrying Value	$ 2,373	$ 2,405
Year-to-Date Weighted-Avg Interest Rate	6.19%	6.19%