Investments (Details 3) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012 item	Dec. 31, 2011 item
Indemnity
Fair value
Less than 12 months	$ 81	$ 233
12 months or longer	25	14
Total	106	247
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	22	49
Indemnity | Investment grade
Fair value
Less than 12 months	81	229
12 months or longer	22	11
Total	103	240
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	21	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	81	229
12 months or longer	22	11
Total	103	240
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	21	46
Indemnity | Corporate debt securities
Fair value
Less than 12 months	68	220
12 months or longer	15	0
Total	83	220
Unrealized losses
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
No. of holdings	16	41
Indemnity | Commercial mortgage-backed securities (CMBS)
Fair value
Less than 12 months	0	4
12 months or longer	7	9
Total	7	13
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	2	3
Indemnity | Collateralized debt obligations (CDO)
Fair value
Less than 12 months	2
12 months or longer	0
Total	2
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	11	5
12 months or longer	0	2
Total	11	7
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	2	2
Indemnity | Nonredeemable preferred stock
Fair value
Less than 12 months	0	4
12 months or longer	3	3
Total	3	7
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	3
Exchange
Fair value
Less than 12 months	421	831
12 months or longer	155	122
Total	576	953
Unrealized losses
Less than 12 months	12	38
12 months or longer	8	11
Total	20	49
No. of holdings	102	151
Exchange | Investment grade
Fair value
Less than 12 months	321	625
12 months or longer	107	79
Total	428	704
Unrealized losses
Less than 12 months	6	26
12 months or longer	3	9
Total	9	35
No. of holdings	75	109
Exchange | Non-investment grade
Fair value
Less than 12 months	41	38
12 months or longer	9	9
Total	50	47
Unrealized losses
Less than 12 months	1	1
12 months or longer	2	1
Total	3	2
No. of holdings	11	15
Exchange | Fixed maturities
Fair value
Less than 12 months	362	663
12 months or longer	116	88
Total	478	751
Unrealized losses
Less than 12 months	7	27
12 months or longer	5	10
Total	12	37
No. of holdings	86	124
Exchange | U.S. government & agencies
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
Exchange | States & political subdivisions
Fair value
Less than 12 months	43	7
12 months or longer	2	6
Total	45	13
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	1
Total	1	1
No. of holdings	14	3
Exchange | Corporate debt securities
Fair value
Less than 12 months	283	635
12 months or longer	76	50
Total	359	685
Unrealized losses
Less than 12 months	6	27
12 months or longer	4	4
Total	10	31
No. of holdings	59	108
Exchange | Residential mortgage-backed securities (RMBS)
Fair value
Less than 12 months	22	7
12 months or longer	0	0
Total	22	7
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	4	4
Exchange | Commercial mortgage-backed securities (CMBS)
Fair value
Less than 12 months	0	5
12 months or longer	2	0
Total	2	5
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	1
Exchange | Collateralized debt obligations (CDO)
Fair value
Less than 12 months	8	0
12 months or longer	33	32
Total	41	32
Unrealized losses
Less than 12 months	0	0
12 months or longer	1	5
Total	1	5
No. of holdings	5	6
Exchange | Other debt securities
Fair value
Less than 12 months	5	9
12 months or longer	3	0
Total	8	9
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	2	2
Exchange | Nonredeemable preferred stock
Fair value
Less than 12 months	59	168
12 months or longer	39	34
Total	98	202
Unrealized losses
Less than 12 months	5	11
12 months or longer	3	1
Total	$ 8	$ 12
No. of holdings	16	27