DERIVATIVES - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Net Amount Presented in the Balance Sheets	$ 14,122	$ 9,226
Derivative, Net Liability Position, Aggregate Fair Value	10	3
Securities Sold under Agreements to Repurchase	0	573
US Treasury Securities
Derivative [Line Items]
Marketable securities	3,881
Total Return Swap
Derivative [Line Items]
Marketable securities	121
Collateral Contracts [Member]
Derivative [Line Items]
Net Amount Presented in the Balance Sheets	3,281	$ 1,564
S&P 500, Russell 1000, NASDAQ 100 and Emerging Market Indices
Derivative [Line Items]
Initial margin requirements	253
Us Treasury Notes Ultra Long Bonds And Euro Dollar
Derivative [Line Items]
Initial margin requirements	28
Euro Stoxx, FTSE100, EAFE And Topix Indices
Derivative [Line Items]
Initial margin requirements	$ 24