DERIVATIVE INSTRUMENTS - Offsetting of Financial Assets and Derivative Assets (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Offsetting Assets [Line Items]
Gross amount of recognized derivative assets	$ 401	$ 1,080
Gross amount of liabilities offset in balance sheet	0	0
Net amount of derivative assets presented in the balance sheet	401	1,080
Financial instruments, amount not offset	(285)	(698)
Derivative, collateral, obligation to return securities	0	0
Derivative, collateral, obligation to return cash	(114)	(382)
Derivative asset, fair value, amount offset against collateral, subject to master netting agreement	2	0
Derivative asset, not subject to master netting arrangement	142	127
Derivative asset, fair value, amount offset against collateral, not subject to master netting agreement	142	127
Derivative asset, fair value, gross asset including not subject to master netting arrangement	543	1,207
Net amount of derivative assets presented in balance sheet	543	1,207
Derivative asset, fair value, amount offset against collateral	144	127
Gross amounts of recognized financial instruments	1,190	1,720
Gross amounts offset in balance sheet	0	0
Net amounts of assets presented in balance sheet	1,190	1,720
Carrying value of financial instruments not offset in balance sheet	(285)	(698)
Securities collateral, not offset in balance sheet	0	0
Cash collateral, not offset in balance sheet	(761)	(895)
Financial instruments, amount offset against collateral	144	127
Securities lending and similar arrangements
Offsetting Assets [Line Items]
Gross amounts of recognized financial instruments	647	513
Gross amounts offset in balance sheet	0	0
Net amounts of assets presented in balance sheet	647	513
Carrying value of financial instruments not offset in balance sheet	0	0
Securities collateral, not offset in balance sheet	0	0
Cash collateral, not offset in balance sheet	(647)	(513)
Financial instruments, amount offset against collateral	$ 0	$ 0