Fair Value of Assets and Liabilities (Level 3 Assets and Liabilities) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Assets
Balance at beginning of period	$ 509	$ 708	$ 514	$ 720
Total gains (losses) included in: Net income	2	5	16	4
Total gains (losses) included in: OCI	4	3	7	14
Transfers into Level 3	0	0	15	34
Transfers out of Level 3	(34)	(217)	(58)	(290)
Purchases	20	33	57	108
Sales	(1)	(6)	(39)	(27)
Issues	0	0	0	0
Settlements	(9)	(26)	(21)	(63)
Balance at end of period	491	500	491	500
Liabilities
Balance at beginning of period	(284)	(304)	(289)	(299)
Total gains (losses) included in: net income	(8)	(2)	(5)	(10)
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	(1)	(1)	(2)
Settlements	2	1	5	5
Balance at end of period	(290)	(306)	(290)	(306)
Fixed income securities
Assets
Balance at beginning of period	433	662	439	666
Total gains (losses) included in: Net income	1	1	7	16
Total gains (losses) included in: OCI	3	3	4	11
Transfers into Level 3	0	0	15	34
Transfers out of Level 3	(34)	(217)	(58)	(290)
Purchases	20	11	57	81
Sales	(1)	(6)	(30)	(27)
Issues	0	0	0	0
Settlements	(9)	(26)	(21)	(63)
Balance at end of period	413	428	413	428
Municipal
Assets
Balance at beginning of period	60	70	59	78
Total gains (losses) included in: Net income	0	1	0	12
Total gains (losses) included in: OCI	0	(1)	1	(6)
Transfers into Level 3	0	0	0	6
Transfers out of Level 3	0	0	0	0
Purchases	0	0	0	0
Sales	0	(4)	0	(24)
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	60	66	60	66
Corporate - public
Assets
Balance at beginning of period	36	41	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	(3)	(6)	(13)	(13)
Purchases	16	3	16	6
Sales	0	(2)	0	(2)
Issues	0	0	0	0
Settlements	(2)	0	(4)	(1)
Balance at end of period	47	36	47	36
Corporate - privately placed
Assets
Balance at beginning of period	250	474	264	447
Total gains (losses) included in: Net income	1	0	6	4
Total gains (losses) included in: OCI	2	2	0	14
Transfers into Level 3	0	0	11	16
Transfers out of Level 3	(14)	(211)	(14)	(276)
Purchases	4	1	7	68
Sales	(1)	0	(30)	0
Issues	0	0	0	0
Settlements	(1)	(24)	(3)	(31)
Balance at end of period	241	242	241	242
ABS - CDO
Assets
Balance at beginning of period	24	33	27	53
Total gains (losses) included in: Net income	0	0	0	0
Total gains (losses) included in: OCI	1	2	3	4
Transfers into Level 3	0	0	4	8
Transfers out of Level 3	(1)	0	(10)	(1)
Purchases	0	0	5	0
Sales	0	0	0	(1)
Issues	0	0	0	0
Settlements	(5)	(2)	(10)	(30)
Balance at end of period	19	33	19	33
ABS - consumer and other
Assets
Balance at beginning of period	63	44	42	44
Total gains (losses) included in: Net income	0	0	0	0
Total gains (losses) included in: OCI	0	0	0	(2)
Transfers into Level 3	0	0	0	3
Transfers out of Level 3	(16)	0	(21)	0
Purchases	0	7	29	7
Sales	0	0	0	0
Issues	0	0	0	0
Settlements	(1)	0	(4)	(1)
Balance at end of period	46	51	46	51
Equity securities
Assets
Balance at beginning of period	75	52	76	60
Total gains (losses) included in: Net income	1	0	7	(16)
Total gains (losses) included in: OCI	1	0	3	3
Transfers into Level 3	0	0	0	0
Transfers out of Level 3	0	0	0	0
Purchases	0	22	0	27
Sales	0	0	(9)	0
Issues	0	0	0	0
Settlements	0	0	0	0
Balance at end of period	77	74	77	74
Free-standing derivatives, net
Assets
Balance at beginning of period	1	(7)	(2)	(7)
Total gains (losses) included in: Net income	0	4	3	4
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	(3)	1	(3)
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	(284)	(304)	(289)	(299)
Total gains (losses) included in: net income	(8)	(2)	(5)	(10)
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	(1)	(1)	(2)
Settlements	2	1	5	5
Balance at end of period	$ (290)	$ (306)	$ (290)	$ (306)