SIGNIFICANT TRANSACTIONS - Narrative (Details) - USD ($)	7 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Jun. 03, 2019	May 01, 2018	Dec. 31, 2017
Business Combination Segment Allocation [Line Items]
Estimated liability based on present value of future payments	$ 2,040,024,000	$ 1,677,717,000			$ 1,361,953,000
Life Business
Business Combination Segment Allocation [Line Items]
Coinsurance basis percentage				100.00%
Ceded commissions for reinsurance				$ 422,400,000
Statutory reserves resulting from reinsurance business acquired, estimate				13,200,000,000
Statutory reserves resulting from reinsurance business acquired, final amount				$ 13,700,000,000
Revenue recognized in earnings		578,000,000.0
Net Income recognized in earnings		49,800,000
Non-recurring transaction costs		$ 5,500,000
Individual Life Business
Business Combination Segment Allocation [Line Items]
Coinsurance basis percentage			100.00%
Ceded commissions for reinsurance			$ 765,700,000
Statutory reserves resulting from reinsurance business acquired, estimate			20,400,000,000
Contingent consideration			49,500,000
Range of outcomes for contingent liability, low			0
Range of outcomes for contingent liability, high			40,000,000
Contingent consideration liability, estimate			$ 37,600,000
Estimated liability based on present value of future payments	500,000
Revenue recognized in earnings	539,800,000
Net Income recognized in earnings	98,800,000
Individual Life Business | Acquisition-related Costs
Business Combination Segment Allocation [Line Items]
Non-recurring transaction costs	$ 12,200,000