INVESTMENTS - Mortgage Loans (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Ending balance	$ (46)
Commercial Real Estate Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	(33)
Current-period provision for expected credit losses	(11)
Write-offs charged against the allowance	0
Recoveries of amounts previously written off	1
Net change in allowance	(10)
Ending balance	(43)
Agricultural Real Estate Portfolio Segment
Financing Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	(3)
Current-period provision for expected credit losses	0
Write-offs charged against the allowance	0
Recoveries of amounts previously written off	0
Net change in allowance	0
Ending balance	$ (3)