Investments (Details 3) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013 Holdings	Dec. 31, 2012 Holdings
Indemnity
Fair value
Less than 12 months	$ 169	$ 92
12 months or longer	3	6
Total	172	98
Unrealized losses
Less than 12 months	2	0
12 months or longer	0	1
Total	2	1
No. of holdings	36	19
Indemnity | Investment grade
Fair value
Less than 12 months	132	55
12 months or longer	0	3
Total	132	58
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	0
Total	1	0
No. of holdings	29	12
Indemnity | Non-investment grade
Fair value
Less than 12 months	6	4
12 months or longer	0	0
Total	6	4
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	1
Indemnity | Fixed maturities
Fair value
Less than 12 months	138	59
12 months or longer	0	3
Total	138	62
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	0
Total	1	0
No. of holdings	30	13
Indemnity | States & political subdivisions
Fair value
Less than 12 months	16
12 months or longer	0
Total	16
Unrealized losses
Less than 12 months	0
12 months or longer	0
Total	0
No. of holdings	7
Indemnity | Corporate debt securities
Fair value
Less than 12 months	122	59
12 months or longer	0	0
Total	122	59
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	0
Total	1	0
No. of holdings	23	12
Indemnity | Commercial mortgage-backed securities
Fair value
Less than 12 months		0
12 months or longer		3
Total		3
Unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
No. of holdings		1
Indemnity | Nonredeemable preferred stock
Fair value
Less than 12 months	6	7
12 months or longer	3	3
Total	9	10
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	1
Total	0	1
No. of holdings	4	4
Indemnity | Common stock
Fair value
Less than 12 months	25	26
12 months or longer	0	0
Total	25	26
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	0
Total	1	0
No. of holdings	2	2
Exchange
Fair value
Less than 12 months	2,243	694
12 months or longer	33	48
Total	2,276	742
Unrealized losses
Less than 12 months	95	7
12 months or longer	2	1
Total	97	8
No. of holdings	347	77
Exchange | Investment grade
Fair value
Less than 12 months	1,713	296
12 months or longer	18	24
Total	1,731	320
Unrealized losses
Less than 12 months	72	4
12 months or longer	1	0
Total	73	4
No. of holdings	305	53
Exchange | Non-investment grade
Fair value
Less than 12 months	98	20
12 months or longer	0	6
Total	98	26
Unrealized losses
Less than 12 months	4	1
12 months or longer	0	0
Total	4	1
No. of holdings	20	8
Exchange | Fixed maturities
Fair value
Less than 12 months	1,811	316
12 months or longer	18	30
Total	1,829	346
Unrealized losses
Less than 12 months	76	5
12 months or longer	1	0
Total	77	5
No. of holdings	325	61
Exchange | U.S. government & agencies
Fair value
Less than 12 months	151	80
12 months or longer	0	0
Total	151	80
Unrealized losses
Less than 12 months	5	1
12 months or longer	0	0
Total	5	1
No. of holdings	12	7
Exchange | States & political subdivisions
Fair value
Less than 12 months	284	23
12 months or longer	0	0
Total	284	23
Unrealized losses
Less than 12 months	13	0
12 months or longer	0	0
Total	13	0
No. of holdings	65	11
Exchange | Foreign government securities
Fair value
Less than 12 months	13
12 months or longer	0
Total	13
Unrealized losses
Less than 12 months	1
12 months or longer	0
Total	1
No. of holdings	2
Exchange | Corporate debt securities
Fair value
Less than 12 months	1,196	152
12 months or longer	11	9
Total	1,207	161
Unrealized losses
Less than 12 months	52	3
12 months or longer	1	0
Total	53	3
No. of holdings	217	31
Exchange | Residential mortgage-backed securities
Fair value
Less than 12 months	122	56
12 months or longer	7	0
Total	129	56
Unrealized losses
Less than 12 months	4	1
12 months or longer	0	0
Total	4	1
No. of holdings	21	9
Exchange | Commercial mortgage-backed securities
Fair value
Less than 12 months	15
12 months or longer	0
Total	15
Unrealized losses
Less than 12 months	1
12 months or longer	0
Total	1
No. of holdings	3
Exchange | Collateralized debt obligations
Fair value
Less than 12 months		0
12 months or longer		21
Total		21
Unrealized losses
Less than 12 months		0
12 months or longer		0
Total		0
No. of holdings		1
Exchange | Other debt securities
Fair value
Less than 12 months	30	5
12 months or longer	0	0
Total	30	5
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	5	2
Exchange | Nonredeemable preferred stock
Fair value
Less than 12 months	110	64
12 months or longer	15	18
Total	125	82
Unrealized losses
Less than 12 months	3	0
12 months or longer	1	1
Total	4	1
No. of holdings	19	13
Exchange | Common stock
Fair value
Less than 12 months	322	314
12 months or longer	0	0
Total	322	314
Unrealized losses
Less than 12 months	16	2
12 months or longer	0	0
Total	$ 16	$ 2
No. of holdings	3	3