DEBT AND OTHER OBLIGATIONS - Non-Recourse Funding Obligations (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Outstanding Principal	$ 2,926,940	$ 2,944,940
Carrying Value	2,934,565	2,952,822
Golden Gate Captive Insurance Company
Debt Instrument [Line Items]
Outstanding Principal	1,981,000	2,014,000
Carrying Value	$ 1,981,000	$ 2,014,000
Year-to-Date Weighted-Avg Interest Rate	4.75%	4.75%
Golden Gate I I
Debt Instrument [Line Items]
Outstanding Principal	$ 309,849	$ 309,849
Carrying Value	$ 255,340	$ 255,132
Year-to-Date Weighted-Avg Interest Rate	3.77%	3.11%
Golden Gate V Vermont Captive Insurance Company
Debt Instrument [Line Items]
Outstanding Principal	$ 635,000	$ 620,000
Carrying Value	$ 695,836	$ 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	$ 2,389	$ 2,405
Year-to-Date Weighted-Avg Interest Rate	6.19%	6.19%