Fair Value of Assets and Liabilities (Level 3 Assets and Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Assets
Balance at beginning of period	$ 522	$ 743	$ 514	$ 720
Total gains (losses) included in: Net income	9	0	14	(1)
Total gains (losses) included in: OCI	(5)	13	3	11
Transfers into Level 3	12	31	15	34
Transfers out of Level 3	(12)	(61)	(24)	(73)
Purchases	24	15	37	75
Sales	(37)	(5)	(38)	(21)
Issues	0	0	0	0
Settlements	(4)	(28)	(12)	(37)
Balance at end of period	509	708	509	708
Liabilities
Balance at beginning of period	(285)	(313)	(289)	(299)
Total gains (losses) included in: net income	0	7	3	(8)
Total gains (losses) included in: OCI	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issues	0	0	(1)	(1)
Settlements	1	2	3	4
Balance at end of period	(284)	(304)	(284)	(304)
Fixed income securities
Assets
Balance at beginning of period	443	694	439	666
Total gains (losses) included in: Net income	6	3	6	15
Total gains (losses) included in: OCI	(7)	13	1	8
Transfers into Level 3	12	31	15	34
Transfers out of Level 3	(12)	(61)	(24)	(73)
Purchases	24	15	37	70
Sales	(29)	(5)	(29)	(21)
Issues	0	0	0	0
Settlements	(4)	(28)	(12)	(37)
Balance at end of period	433	662	433	662
Municipal
Assets
Balance at beginning of period	60	66	59	78
Total gains (losses) included in: Net income	0	0	0	11
Total gains (losses) included in: OCI	0	3	1	(5)
Transfers into Level 3	0	6	0	6
Transfers out of Level 3	0	0	0	0
Purchases	0	0	0	0
Sales	0	(5)	0	(20)
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	60	70	60	70
Corporate - public
Assets
Balance at beginning of period	36	38	47	44
Total gains (losses) included in: Net income	0	0	1	0
Total gains (losses) included in: OCI	0	0	0	1
Transfers into Level 3	0	0	0	1
Transfers out of Level 3	0	0	(10)	(7)
Purchases	0	3	0	3
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	0	0	(2)	(1)
Balance at end of period	36	41	36	41
Corporate - privately placed
Assets
Balance at beginning of period	268	497	264	447
Total gains (losses) included in: Net income	5	3	5	4
Total gains (losses) included in: OCI	(7)	8	(2)	12
Transfers into Level 3	11	16	11	16
Transfers out of Level 3	0	(60)	0	(65)
Purchases	3	12	3	67
Sales	(29)	0	(29)	0
Issues	0	0	0	0
Settlements	(1)	(2)	(2)	(7)
Balance at end of period	250	474	250	474
ABS - CDO
Assets
Balance at beginning of period	32	50	27	53
Total gains (losses) included in: Net income	1	0	0	0
Total gains (losses) included in: OCI	0	3	2	2
Transfers into Level 3	1	6	4	8
Transfers out of Level 3	(9)	(1)	(9)	(1)
Purchases	0	0	5	0
Sales	0	0	0	(1)
Issues	0	0	0	0
Settlements	(1)	(25)	(5)	(28)
Balance at end of period	24	33	24	33
ABS - consumer and other
Assets
Balance at beginning of period	47	43	42	44
Total gains (losses) included in: Net income	0	0	0	0
Total gains (losses) included in: OCI	0	(1)	0	(2)
Transfers into Level 3	0	3	0	3
Transfers out of Level 3	(3)	0	(5)	0
Purchases	21	0	29	0
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	(2)	(1)	(3)	(1)
Balance at end of period	63	44	63	44
Equity securities
Assets
Balance at beginning of period	80	56	76	60
Total gains (losses) included in: Net income	1	(4)	6	(16)
Total gains (losses) included in: OCI	2	0	2	3
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Purchases	0	0	0	5
Sales	(8)	0	(9)	0
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	75	52	75	52
Free-standing derivatives, net
Assets
Balance at beginning of period	(1)	(8)	(2)	(7)
Total gains (losses) included in: Net income	2	1	3	0
Total gains (losses) included in: OCI	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	1	(7)	1	(7)
Other assets
Assets
Balance at beginning of period		1	1	1
Total gains (losses) included in: Net income		0	(1)	0
Total gains (losses) included in: OCI		0	0	0
Transfers into Level 3		0	0	0
Transfers out of Level 3		0	0	0
Purchases		0	0	0
Sales		0	0	0
Issues		0	0	0
Settlements		0	0	0
Balance at end of period	0	1	0	1
Contractholder funds: Derivatives embedded in life and annuity contracts
Liabilities
Balance at beginning of period	(285)	(313)	(289)	(299)
Total gains (losses) included in: net income	0	7	3	(8)
Total gains (losses) included in: OCI	0	0	0	0
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Purchases	0	0	0	0
Sales	0	0	0	0
Issues	0	0	(1)	(1)
Settlements	1	2	3	4
Balance at end of period	$ (284)	$ (304)	$ (284)	$ (304)