Investments (Details 3) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012 item	Dec. 31, 2011 item
Indemnity
Fair value
Less than 12 months	$ 58	$ 233
12 months or longer	13	14
Total	71	247
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	16	49
Indemnity | Investment grade
Fair value
Less than 12 months	55	229
12 months or longer	10	11
Total	65	240
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	14	46
Indemnity | Non-investment grade
Fair value
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	0	0
Indemnity | Fixed maturities
Fair value
Less than 12 months	55	229
12 months or longer	10	11
Total	65	240
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	14	46
Indemnity | Corporate debt securities
Fair value
Less than 12 months	54	220
12 months or longer	5	0
Total	59	220
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	12	41
Indemnity | Commercial mortgage-backed securities (CMBS)
Fair value
Less than 12 months	0	4
12 months or longer	5	9
Total	5	13
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	3
Indemnity | Collateralized debt obligations (CDO)
Fair value
Less than 12 months	1
12 months or longer	0
Total	1
Unrealized losses
Less than 12 months	0
12 months or longer	0
Total	0
No. of holdings	1
Indemnity | Other debt securities
Fair value
Less than 12 months		5
12 months or longer		2
Total		7
Unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
No. of holdings		2
Indemnity | Nonredeemable preferred stock
Fair value
Less than 12 months	3	4
12 months or longer	3	3
Total	6	7
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	2	3
Exchange
Fair value
Less than 12 months	155	831
12 months or longer	87	122
Total	242	953
Unrealized losses
Less than 12 months	3	38
12 months or longer	4	11
Total	7	49
No. of holdings	45	151
Exchange | Investment grade
Fair value
Less than 12 months	79	625
12 months or longer	45	79
Total	124	704
Unrealized losses
Less than 12 months	2	26
12 months or longer	1	9
Total	3	35
No. of holdings	24	109
Exchange | Non-investment grade
Fair value
Less than 12 months	37	38
12 months or longer	9	9
Total	46	47
Unrealized losses
Less than 12 months	1	1
12 months or longer	1	1
Total	2	2
No. of holdings	8	15
Exchange | Fixed maturities
Fair value
Less than 12 months	116	663
12 months or longer	54	88
Total	170	751
Unrealized losses
Less than 12 months	3	27
12 months or longer	2	10
Total	5	37
No. of holdings	32	124
Exchange | States & political subdivisions
Fair value
Less than 12 months	5	7
12 months or longer	0	6
Total	5	13
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	1
Total	1	1
No. of holdings	2	3
Exchange | Corporate debt securities
Fair value
Less than 12 months	90	635
12 months or longer	23	50
Total	113	685
Unrealized losses
Less than 12 months	2	27
12 months or longer	2	4
Total	4	31
No. of holdings	24	108
Exchange | Residential mortgage-backed securities (RMBS)
Fair value
Less than 12 months	10	7
12 months or longer	0	0
Total	10	7
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	4
Exchange | Commercial mortgage-backed securities (CMBS)
Fair value
Less than 12 months		5
12 months or longer		0
Total		5
Unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
No. of holdings		1
Exchange | Collateralized debt obligations (CDO)
Fair value
Less than 12 months	6	0
12 months or longer	31	32
Total	37	32
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	5
Total	0	5
No. of holdings	4	6
Exchange | Other debt securities
Fair value
Less than 12 months	5	9
12 months or longer	0	0
Total	5	9
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	2
Exchange | Nonredeemable preferred stock
Fair value
Less than 12 months	39	168
12 months or longer	33	34
Total	72	202
Unrealized losses
Less than 12 months	0	11
12 months or longer	2	1
Total	$ 2	$ 12
No. of holdings	13	27