COMMITMENT AND CONTINGENT LIABILITIES - OBLIGATION UNDER FUNDING AGREEMENTS (Details) $ / policy in Millions, $ in Millions	1 Months Ended	9 Months Ended	12 Months Ended	19 Months Ended
	Feb. 29, 2016 $ / policy	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jan. 31, 2013 fund
Restructuring Cost and Reserve [Line Items]
Unaccrued amounts of reasonably possible range of losses		$ 90
Advances from Federal Home Loan Banks		3,000	$ 3,000
Proceeds from FHLBank Borrowings, Financing Activities		4,500	6,762
Payments of FHLBank Borrowings, Financing Activities		4,500	6,000
Letters of credit outstanding		18
Equity financing arrangements with Limited Partnerships		761
Equity financing arrangements with affiliates		197
Mortgage loans on real estate		379
Federal Home Loan Bank of New York Short-Term Funding Agreements Maturing in Less than One Month
Restructuring Cost and Reserve [Line Items]
Advances from Federal Home Loan Banks		500	500
Proceeds from FHLBank Borrowings, Financing Activities		4,500	6,000
Payments of FHLBank Borrowings, Financing Activities		4,500	6,000
Federal Home Loan Bank of New York Long-Term Funding Agreements Maturing in Less than Four Years
Restructuring Cost and Reserve [Line Items]
Advances from Federal Home Loan Banks		1,621	1,244
Proceeds from FHLBank Borrowings, Financing Activities		0	324
Payments of FHLBank Borrowings, Financing Activities		0	0
Federal Home Loan Bank of New York Long-Term Funding Agreements Maturing in Less than Five Years
Restructuring Cost and Reserve [Line Items]
Advances from Federal Home Loan Banks		98	377
Proceeds from FHLBank Borrowings, Financing Activities		0	303
Payments of FHLBank Borrowings, Financing Activities		0	0
Federal Home Loan Bank of New York Long-Term Funding Agreements Maturing in Greater than Five Years
Restructuring Cost and Reserve [Line Items]
Advances from Federal Home Loan Banks		781	879
Proceeds from FHLBank Borrowings, Financing Activities		0	135
Payments of FHLBank Borrowings, Financing Activities		0	0
Federal Home Loan Bank of New York Long-Term Funding Agreements
Restructuring Cost and Reserve [Line Items]
Advances from Federal Home Loan Banks		2,500	2,500
Proceeds from FHLBank Borrowings, Financing Activities		0	762
Payments of FHLBank Borrowings, Financing Activities		$ 0	$ 0
Sivolella Litigation
Restructuring Cost and Reserve [Line Items]
Loss contingency, number of funds involved in lawsuit | fund				12
Brach Family Foundation Litigation
Restructuring Cost and Reserve [Line Items]
Liability for future policy benefits, issue age	70 years
Liability for future policy benefits, amount per policy | $ / policy	1