MORTGAGE LOANS - Additional Information (Details)	1 Months Ended	11 Months Ended	12 Months Ended
	Jan. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 USD ($) loan loan_category	Dec. 31, 2014 USD ($) loan	Dec. 31, 2016 USD ($) loan	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Mortgage loans
Number of nonperforming loans which have been restructured | loan			0
Maximum
Mortgage loans
Loan-to-value ratio with participating interest (as a percent) (up to)					85.00%
Commercial mortgage loans
Mortgage loans
Number of loan categories | loan_category			2
Successor
Mortgage loans
Nonperforming loans which have been foreclosed					$ 1,000,000
Successor | Commercial mortgage loans
Mortgage loans
Mortgage loans having participation feature					595,200,000	$ 449,200,000
Income recognized on participating mortgage loans		$ 29,800,000	$ 16,700,000
Nonperforming mortgage loans, foreclosed properties and restructured loans pursuant to pooling and servicing agreements					1,500,000	4,700,000
Assets accepted or agreed to be accepted on mortgage loans accounted for as troubled debt restructurings		15,800,000
Principal amount of loans accounted for as troubled debt restructurings satisfied by acceptance of assets		21,100,000
Assets accepted or agreed to be accepted on mortgage loans accounted for as troubled debt restructurings, amount related foreclosures		3,700,000
Loans not subject to a pooling and servicing agreement which are either nonperforming or restructured					$ 1,500,000
Loans subject to a pooling and servicing agreement which are either nonperforming or restructured | loan					0
Allowance for credit losses	$ 0	0	0		$ 724,000	$ 0
Change in the allowance for credit losses
Beginning balance		0	0
Charge offs		(2,561,000)	(4,682,000)
Recoveries		(638,000)	0
Provision		3,199,000	5,406,000
Ending balance	0	0	$ 724,000
Predecessor | Commercial mortgage loans
Mortgage loans
Income recognized on participating mortgage loans	100,000
Nonperforming mortgage loans, foreclosed properties and restructured loans pursuant to pooling and servicing agreements							$ 24,500,000
Assets accepted or agreed to be accepted on mortgage loans accounted for as troubled debt restructurings	11,300,000			$ 33,000,000
Principal amount of loans accounted for as troubled debt restructurings satisfied by acceptance of assets	13,800,000			$ 41,700,000
Nonperforming mortgage loans, foreclosed properties and restructured loans to invested assets (as a percent)							0.05%
Number of mortgage loans permanently impaired | loan				1
Principal amount of impaired loans accounted for as troubled debt restructurings				$ 12,600,000
Impaired mortgage loans accounted for as troubled debt restructurings							$ 7,300,000
Reduction in the entity's investment in mortgage loans, net of existing allowances for mortgage loan losses				10,300,000
Allowance for credit losses	5,720,000	2,500,000		5,720,000			$ 5,720,000
Change in the allowance for credit losses
Beginning balance	5,720,000	$ 2,500,000
Charge offs	(861,000)
Recoveries	(2,359,000)
Provision	0
Ending balance	$ 2,500,000			$ 5,720,000