REVISION OF PRIOR PERIOD FINANCIAL STATEMENTS - CASH FLOW DISCLOSURES (Details) - USD ($) $ in Millions	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flow from operating activities:
Net income (loss)	$ (382)	$ (1,928)	$ (109)	$ 143	$ 1,621	$ (83)	$ (2,037)	$ 1,538	$ (2,419)	$ 1,681	$ 3,377	$ 686	$ 1,046
Policy charges and fee income	(900)	(883)	(861)	(852)	(834)	(830)	(1,744)	(1,664)	(2,644)	(2,516)	(3,294)	(3,311)	(3,266)
Interest credited to policyholders’ account balances	259		255	233	199	249			754	681	921	905
(Income) loss related to derivative instruments	$ 2,006	285	815	$ 368	(1,771)	355	1,100	(1,416)	3,106	(1,048)	(870)	1,337	1,173
Changes in:
Deferred policy acquisition costs			74			92	110	(42)	(129)	42	322	48	(248)
Future policy benefits			(200)			238	349	1,293	(58)	1,146	1,522		633
Reinsurance recoverable									20	(361)
Current and deferred income taxes			(71)			(204)	(630)	193	(264)	640	(653)	(753)	43
Other, net			(52)						123	617
Net cash provided by (used in) operating activities			(21)			18	1,190	(75)	$ 1,614	994	1,077	(461)	(324)
As Previously Reported
Cash flow from operating activities:
Net income (loss)		(1,958)	(40)		1,613	(54)	(2,091)	1,559		1,677	3,394	706	1,060
Policy charges and fee income		(904)	(869)		(846)	(852)	(1,773)	(1,698)		(2,626)	(3,334)	(3,344)	(3,291)
Interest credited to policyholders’ account balances			338		208	279				1,008	1,040	1,029
(Income) loss related to derivative instruments		312	777		(1,763)	362	1,172	(1,362)		(1,376)	(890)	1,211	1,174
Changes in:
Deferred policy acquisition costs			10			29	89	20		15	268	52	(243)
Future policy benefits			(191)			241	396	1,303		1,289	1,511		631
Current and deferred income taxes			(52)			(188)	(645)	204		639	(664)	(742)	50
Other, net			(122)
Net cash provided by (used in) operating activities			(21)			18	1,190	(75)		994	1,077	(461)	(324)
Impact of Revisions
Cash flow from operating activities:
Net income (loss)		30	(69)		8	(29)	54	(21)		4	(17)	(20)	(14)
Policy charges and fee income		21	8		12	22	29	34		110	40	33	25
Interest credited to policyholders’ account balances			(83)		(9)	(30)				(327)	(119)	(124)
(Income) loss related to derivative instruments		$ (27)	38		$ (8)	(7)	(72)	(54)		328	20	126	(1)
Changes in:
Deferred policy acquisition costs			64			63	21	(62)		27	54	(4)	(5)
Future policy benefits			(9)			(3)	(47)	(10)		(143)	11		2
Current and deferred income taxes			(19)			(16)	15	(11)		1	11	(11)	(7)
Other, net			70
Net cash provided by (used in) operating activities			$ 0			$ 0	$ 0	$ 0		$ 0	$ 0	$ 0	$ 0