Fair Value Measurements (excluding Consolidated Investment Entities) - Level 3 Financial Instruments (Details) - Assets measured on recurring basis - Level 3 - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Assets held in separate accounts
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	$ 5	$ 4
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	18	3
Issuances	0	0
Sales	(3)	0
Settlements	0	0
Transfers in to Level 3	2	2
Transfers out of Level 3	(11)	(4)
Assets, Fair Value, ending balance	11	5
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Other derivatives
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	72	47
Total Realized/Unrealized Gains (Losses) Included in Net income	78	9
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	31	26
Issuances	0	0
Sales	0	0
Settlements	(22)	(10)
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	159	72
Change in Unrealized Gains (Losses) in Earnings	87	25
FIA
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	(42)	(41)
Total Realized/Unrealized Gains (Losses) Included in Net income	(2)	(3)
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	0	0
Issuances	(1)	(1)
Sales	0	0
Settlements	5	3
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	(40)	(42)
Change in Unrealized Gains (Losses) in Earnings	0	0
IUL
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	(81)	(53)
Total Realized/Unrealized Gains (Losses) Included in Net income	(87)	(12)
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	0	0
Issuances	(35)	(29)
Sales	0	0
Settlements	44	13
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	(159)	(81)
Change in Unrealized Gains (Losses) in Earnings	0	0
GMWBL/GMWB/GMAB
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	(18)	(24)
Total Realized/Unrealized Gains (Losses) Included in Net income	10	9
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	0	0
Issuances	(2)	(3)
Sales	0	0
Settlements	0	0
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	(10)	(18)
Change in Unrealized Gains (Losses) in Earnings	0	0
Stabilizer / MCG
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	(150)	(161)
Total Realized/Unrealized Gains (Losses) Included in Net income	57	15
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	0	0
Issuances	(4)	(4)
Sales	0	0
Settlements	0	0
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	(97)	(150)
Change in Unrealized Gains (Losses) in Earnings	0	0
U.S. corporate public securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	12	6
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	29	0
Issuances	0	0
Sales	0	(1)
Settlements	(2)	(2)
Transfers in to Level 3	18	9
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	57	12
Change In Unrealized Gains (Losses) Included in Earnings	0	0
U.S. corporate private securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	913	720
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	(16)	(4)
Purchases	128	302
Issuances	0	0
Sales	(5)	(23)
Settlements	(40)	(135)
Transfers in to Level 3	130	63
Transfers out of Level 3	(15)	(18)
Assets, Fair Value, ending balance	1,127	913
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Foreign corporate public securities and foreign governments
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	12	12
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	1	0
Purchases	0	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	11	12
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Foreign corporate private securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	305	294
Total Realized/Unrealized Gains (Losses) Included in Net income	(14)	(2)
Total Realized/Unrealized Gains (Losses) Included in OCI	46	(12)
Purchases	57	0
Issuances	0	0
Sales	(1)	0
Settlements	(44)	(52)
Transfers in to Level 3	0	61
Transfers out of Level 3	(88)	(8)
Assets, Fair Value, ending balance	169	305
Change In Unrealized Gains (Losses) Included in Earnings	(14)	(2)
Residential mortgage-backed securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	57	76
Total Realized/Unrealized Gains (Losses) Included in Net income	(14)	(5)
Total Realized/Unrealized Gains (Losses) Included in OCI	(1)	1
Purchases	5	0
Issuances	0	0
Sales	(8)	(12)
Settlements	(1)	(1)
Transfers in to Level 3	2	0
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	42	57
Change In Unrealized Gains (Losses) Included in Earnings	(14)	(12)
Commercial mortgage-backed
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	16	19
Total Realized/Unrealized Gains (Losses) Included in Net income	0	(1)
Total Realized/Unrealized Gains (Losses) Included in OCI	0	(1)
Purchases	17	4
Issuances	0	0
Sales	0	0
Settlements	0	(7)
Transfers in to Level 3	0	1
Transfers out of Level 3	(16)	(1)
Assets, Fair Value, ending balance	17	16
Change In Unrealized Gains (Losses) Included in Earnings	0	(1)
Other asset-backed securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	53	33
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	(1)	(1)
Purchases	72	31
Issuances	0	0
Sales	0	0
Settlements	(3)	(3)
Transfers in to Level 3	0	1
Transfers out of Level 3	(31)	(10)
Assets, Fair Value, ending balance	92	53
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Fixed maturities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	1,368	1,160
Total Realized/Unrealized Gains (Losses) Included in Net income	(28)	(8)
Total Realized/Unrealized Gains (Losses) Included in OCI	29	(17)
Purchases	308	337
Issuances	0	0
Sales	(14)	(36)
Settlements	(90)	(200)
Transfers in to Level 3	150	135
Transfers out of Level 3	(150)	(37)
Assets, Fair Value, ending balance	1,515	1,368
Change In Unrealized Gains (Losses) Included in Earnings	(28)	(15)
Equity securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	94	92
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	(2)	(2)
Purchases	8	0
Issuances	0	0
Sales	(2)	0
Settlements	0	0
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	102	94
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Short-term investments and cash equivalents
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	0	0
Total Realized/Unrealized Gains (Losses) Included in Net income		0
Total Realized/Unrealized Gains (Losses) Included in OCI		0
Purchases		0
Issuances		0
Sales		0
Settlements		0
Transfers in to Level 3		0
Transfers out of Level 3		0
Assets, Fair Value, ending balance		0
Change In Unrealized Gains (Losses) Included in Earnings		0
Held for sale | Other derivatives
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	34	6
Total Realized/Unrealized Gains (Losses) Included in Net income	133	4
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	41	27
Issuances	0	0
Sales	0	0
Settlements	(117)	(3)
Transfers in to Level 3	4	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	95	34
Change in Unrealized Gains (Losses) in Earnings	57	28
Held for sale | FIA
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	(1,987)	(1,779)
Total Realized/Unrealized Gains (Losses) Included in Net income	(297)	(160)
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	0	0
Issuances	(153)	(237)
Sales	0	0
Settlements	195	189
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	(2,242)	(1,987)
Change in Unrealized Gains (Losses) in Earnings	0	0
Held for sale | GMWBL/GMWB/GMAB
Derivatives Rollforward:
Fair Value, Derivatives, beginning balance	(1,512)	(1,849)
Total Realized/Unrealized Gains (Losses) Included in Net income	500	484
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	0	0
Issuances	(146)	(148)
Sales	0	0
Settlements	0	1
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Fair Value, Derivatives, ending balance	(1,158)	(1,512)
Change in Unrealized Gains (Losses) in Earnings	0	0
Held for sale | U.S. corporate public securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	10	1
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	(1)	0
Purchases	15	0
Issuances	0	0
Sales	(10)	(1)
Settlements	0	(1)
Transfers in to Level 3	6	11
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	22	10
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Held for sale | U.S. corporate private securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	406	321
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	(9)	(3)
Purchases	71	127
Issuances	0	0
Sales	(1)	(14)
Settlements	(16)	(42)
Transfers in to Level 3	44	18
Transfers out of Level 3	(10)	(7)
Assets, Fair Value, ending balance	503	406
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Held for sale | Foreign corporate public securities and foreign governments
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	0	1
Total Realized/Unrealized Gains (Losses) Included in Net income		(1)
Total Realized/Unrealized Gains (Losses) Included in OCI		0
Purchases		0
Issuances		0
Sales		0
Settlements		0
Transfers in to Level 3		0
Transfers out of Level 3		0
Assets, Fair Value, ending balance		0
Change In Unrealized Gains (Losses) Included in Earnings		(1)
Held for sale | Foreign corporate private securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	136	136
Total Realized/Unrealized Gains (Losses) Included in Net income	(10)	(1)
Total Realized/Unrealized Gains (Losses) Included in OCI	21	(8)
Purchases	13	0
Issuances	0	0
Sales	0	0
Settlements	(14)	(23)
Transfers in to Level 3	0	19
Transfers out of Level 3	(21)	(3)
Assets, Fair Value, ending balance	83	136
Change In Unrealized Gains (Losses) Included in Earnings	(10)	(1)
Held for sale | Residential mortgage-backed securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	15	21
Total Realized/Unrealized Gains (Losses) Included in Net income	(3)	(3)
Total Realized/Unrealized Gains (Losses) Included in OCI	1	0
Purchases	22	0
Issuances	0	0
Sales	0	(3)
Settlements	(1)	0
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	32	15
Change In Unrealized Gains (Losses) Included in Earnings	(3)	(3)
Held for sale | Commercial mortgage-backed
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	8	12
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	10	0
Issuances	0	0
Sales	0	0
Settlements	0	(4)
Transfers in to Level 3	0	0
Transfers out of Level 3	(8)	0
Assets, Fair Value, ending balance	10	8
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Held for sale | Other asset-backed securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	31	11
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	38	14
Issuances	0	0
Sales	0	0
Settlements	(2)	(3)
Transfers in to Level 3	1	9
Transfers out of Level 3	(21)	0
Assets, Fair Value, ending balance	47	31
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Held for sale | Fixed maturities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	606	503
Total Realized/Unrealized Gains (Losses) Included in Net income	(13)	(5)
Total Realized/Unrealized Gains (Losses) Included in OCI	12	(11)
Purchases	169	141
Issuances	0	0
Sales	(11)	(18)
Settlements	(33)	(73)
Transfers in to Level 3	51	57
Transfers out of Level 3	(60)	(10)
Assets, Fair Value, ending balance	697	606
Change In Unrealized Gains (Losses) Included in Earnings	(13)	(5)
Held for sale | Equity securities
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	5	5
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	(1)	0
Purchases	5	0
Issuances	0	0
Sales	0	0
Settlements	0	0
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	11	5
Change In Unrealized Gains (Losses) Included in Earnings	0	0
Held for sale | Short-term investments and cash equivalents
Fixed Maturities and Equity Securities Rollforward:
Assets, Fair Value, beginning balance	5	0
Total Realized/Unrealized Gains (Losses) Included in Net income	0	0
Total Realized/Unrealized Gains (Losses) Included in OCI	0	0
Purchases	0	5
Issuances	0
Sales	(5)	0
Settlements	0	0
Transfers in to Level 3	0	0
Transfers out of Level 3	0	0
Assets, Fair Value, ending balance	0	5
Change In Unrealized Gains (Losses) Included in Earnings	$ 0	$ 0