Investments (Details 3) (USD $) In Millions, unless otherwise specified	Jun. 30, 2011	Dec. 31, 2010
Indemnity
Fair value
Less than 12 months	$ 134	$ 98
12 months or longer	0	1
Total	134	99
Unrealized losses
Less than 12 months	0	2
12 months or longer	0	0
Total	0	2
No. of holdings	29	25
Indemnity | Fixed maturities
Fair value
Less than 12 months	131	95
12 months or longer	0	1
Total	131	96
Unrealized losses
Less than 12 months	0	2
12 months or longer	0	0
Total	0	2
No. of holdings	28	24
Indemnity | U.S. government & agencies
Fair value
Less than 12 months		25
12 months or longer		0
Total		25
Unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
No. of holdings		1
Indemnity | States & political subdivisions
Fair value
Less than 12 months	24	39
12 months or longer	0	1
Total	24	40
Unrealized losses
Less than 12 months	0	2
12 months or longer	0	0
Total	0	2
No. of holdings	11	20
Indemnity | Corporate debt securities
Fair value
Less than 12 months	78	31
12 months or longer	0	0
Total	78	31
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	12	3
Indemnity | Other debt securities
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
Indemnity | Commercial mortgage-backed securities (CMBS)
Fair value
Less than 12 months	24
12 months or longer	0
Total	24
Unrealized losses
Less than 12 months	0
12 months or longer	0
Total	0
No. of holdings	4
Indemnity | Nonredeemable preferred stock
Fair value
Less than 12 months	3	3
12 months or longer	0	0
Total	3	3
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	1
Indemnity | Investment grade
Fair value
Less than 12 months	131	95
12 months or longer	0	1
Total	131	96
Unrealized losses
Less than 12 months	0	2
12 months or longer	0	0
Total	0	2
No. of holdings	28	24
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
Exchange
Fair value
Less than 12 months	580	781
12 months or longer	117	260
Total	697	1,041
Unrealized losses
Less than 12 months	7	18
12 months or longer	9	19
Total	16	37
No. of holdings	129	191
Exchange | Fixed maturities
Fair value
Less than 12 months	527	736
12 months or longer	97	201
Total	624	937
Unrealized losses
Less than 12 months	6	16
12 months or longer	8	14
Total	14	30
No. of holdings	117	176
Exchange | U.S. government & agencies
Fair value
Less than 12 months	25	22
12 months or longer	0	0
Total	25	22
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	3	3
Exchange | States & political subdivisions
Fair value
Less than 12 months	122	299
12 months or longer	4	5
Total	126	304
Unrealized losses
Less than 12 months	2	8
12 months or longer	1	1
Total	3	9
No. of holdings	28	59
Exchange | Foreign government securities
Fair value
Less than 12 months		10
12 months or longer		0
Total		10
Unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
No. of holdings		1
Exchange | Corporate debt securities
Fair value
Less than 12 months	362	398
12 months or longer	57	144
Total	419	542
Unrealized losses
Less than 12 months	4	8
12 months or longer	2	6
Total	6	14
No. of holdings	75	101
Exchange | Residential mortgage-backed securities (RMBS)
Fair value
Less than 12 months	13	6
12 months or longer	3	7
Total	16	13
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	1
Total	0	1
No. of holdings	4	4
Exchange | Commercial mortgage-backed securities (CMBS)
Fair value
Less than 12 months	5	0
12 months or longer	1	12
Total	6	12
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	1
Total	0	1
No. of holdings	2	2
Exchange | Collateralized debt obligations (CDO)
Fair value
Less than 12 months	0	1
12 months or longer	32	33
Total	32	34
Unrealized losses
Less than 12 months	0	0
12 months or longer	5	5
Total	5	5
No. of holdings	5	6
Exchange | Nonredeemable preferred stock
Fair value
Less than 12 months	53	45
12 months or longer	20	59
Total	73	104
Unrealized losses
Less than 12 months	1	2
12 months or longer	1	5
Total	2	7
No. of holdings	12	15
Exchange | Investment grade
Fair value
Less than 12 months	498	703
12 months or longer	85	155
Total	583	858
Unrealized losses
Less than 12 months	6	16
12 months or longer	7	11
Total	13	27
No. of holdings	105	154
Exchange | Non-investment grade
Fair value
Less than 12 months	29	33
12 months or longer	12	46
Total	41	79
Unrealized losses
Less than 12 months	0	0
12 months or longer	1	3
Total	$ 1	$ 3
No. of holdings	12	22