COMMITMENT AND CONTINGENT LIABILITIES - Obligations Under Funding Agreements (Details) $ / policy in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Feb. 29, 2016 $ / policy
Restructuring Cost and Reserve [Line Items]
Funding Agreement, Difference Related To Remaining Amortization	$ 11	$ 12
Unaccrued amounts of reasonably possible range of losses	95
Advances from Federal Home Loan Banks	3,990
Proceeds from FHLBank Borrowings, Financing Activities	4,470
Payments of FHLBank Borrowings, Financing Activities	4,470
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	1,640
Proceeds from FHLBank Borrowings, Financing Activities	4,470
Payments of FHLBank Borrowings, Financing Activities	4,470
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	1,569
Proceeds from FHLBank Borrowings, Financing Activities	0
Payments of FHLBank Borrowings, Financing Activities	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
Proceeds from FHLBank Borrowings, Financing Activities	0
Payments of FHLBank Borrowings, Financing Activities	0
Federal Home Loan Bank of New York Long-Term Funding Agreements
Restructuring Cost and Reserve [Line Items]
Advances from Federal Home Loan Banks	2,350
Proceeds from FHLBank Borrowings, Financing Activities	0
Payments of FHLBank Borrowings, Financing Activities	$ 0
Brach Family Foundation Litigation
Restructuring Cost and Reserve [Line Items]
Liability for future policy benefits, amount per policy | $ / policy			1