Investments (Details 3) (USD $) In Millions, unless otherwise specified	Sep. 30, 2013 Holdings	Dec. 31, 2012 Holdings
Indemnity
Fair value
Less than 12 months	$ 124	$ 92
12 months or longer	16	6
Total	140	98
Unrealized losses
Less than 12 months	3	0
12 months or longer	0	1
Total	3	1
No. of holdings	31	19
Indemnity | Investment grade
Fair value
Less than 12 months	96	55
12 months or longer	10	3
Total	106	58
Unrealized losses
Less than 12 months	2	0
12 months or longer	0	0
Total	2	0
No. of holdings	25	12
Indemnity | Non-investment grade
Fair value
Less than 12 months	0	4
12 months or longer	0	0
Total	0	4
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	0	1
Indemnity | Fixed maturities
Fair value
Less than 12 months	96	59
12 months or longer	10	3
Total	106	62
Unrealized losses
Less than 12 months	2	0
12 months or longer	0	0
Total	2	0
No. of holdings	25	13
Indemnity | States & political subdivisions
Fair value
Less than 12 months	23
12 months or longer	0
Total	23
Unrealized losses
Less than 12 months	1
12 months or longer	0
Total	1
No. of holdings	10
Indemnity | Corporate debt securities
Fair value
Less than 12 months	73	59
12 months or longer	10	0
Total	83	59
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	0
Total	1	0
No. of holdings	15	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	3	7
12 months or longer	6	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	2,056	694
12 months or longer	35	48
Total	2,091	742
Unrealized losses
Less than 12 months	75	7
12 months or longer	3	1
Total	78	8
No. of holdings	335	77
Exchange | Investment grade
Fair value
Less than 12 months	1,561	296
12 months or longer	19	24
Total	1,580	320
Unrealized losses
Less than 12 months	58	4
12 months or longer	2	0
Total	60	4
No. of holdings	289	53
Exchange | Non-investment grade
Fair value
Less than 12 months	92	20
12 months or longer	1	6
Total	93	26
Unrealized losses
Less than 12 months	5	1
12 months or longer	0	0
Total	5	1
No. of holdings	19	8
Exchange | Fixed maturities
Fair value
Less than 12 months	1,653	316
12 months or longer	20	30
Total	1,673	346
Unrealized losses
Less than 12 months	63	5
12 months or longer	2	0
Total	65	5
No. of holdings	308	61
Exchange | U.S. government & agencies
Fair value
Less than 12 months	104	80
12 months or longer	0	0
Total	104	80
Unrealized losses
Less than 12 months	2	1
12 months or longer	0	0
Total	2	1
No. of holdings	7	7
Exchange | States & political subdivisions
Fair value
Less than 12 months	309	23
12 months or longer	0	0
Total	309	23
Unrealized losses
Less than 12 months	12	0
12 months or longer	0	0
Total	12	0
No. of holdings	77	11
Exchange | Foreign government 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
Exchange | Corporate debt securities
Fair value
Less than 12 months	1,116	152
12 months or longer	6	9
Total	1,122	161
Unrealized losses
Less than 12 months	44	3
12 months or longer	1	0
Total	45	3
No. of holdings	199	31
Exchange | Residential mortgage-backed securities
Fair value
Less than 12 months	87	56
12 months or longer	14	0
Total	101	56
Unrealized losses
Less than 12 months	4	1
12 months or longer	1	0
Total	5	1
No. of holdings	18	9
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	32	5
12 months or longer	0	0
Total	32	5
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	0
Total	1	0
No. of holdings	6	2
Exchange | Nonredeemable preferred stock
Fair value
Less than 12 months	165	64
12 months or longer	15	18
Total	180	82
Unrealized losses
Less than 12 months	9	0
12 months or longer	1	1
Total	10	1
No. of holdings	24	13
Exchange | Common stock
Fair value
Less than 12 months	238	314
12 months or longer	0	0
Total	238	314
Unrealized losses
Less than 12 months	3	2
12 months or longer	0	0
Total	$ 3	$ 2
No. of holdings	3	3