Investments (Details 3) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015 Holdings	Dec. 31, 2014 Holdings
Indemnity
Fair value
Less than 12 months	$ 133	$ 202
12 months or longer	3	15
Total	136	217
Unrealized losses
Less than 12 months	3	4
12 months or longer	0	0
Total	3	4
No. of holdings	218	295
Indemnity | Investment grade
Fair value
Less than 12 months	69	146
12 months or longer	3	2
Total	72	148
Unrealized losses
Less than 12 months	1	1
12 months or longer	0	0
Total	1	1
No. of holdings	37	58
Indemnity | Non-investment grade
Fair value
Less than 12 months	51	56
12 months or longer	0	0
Total	51	56
Unrealized losses
Less than 12 months	2	3
12 months or longer	0	0
Total	2	3
No. of holdings	180	236
Indemnity | Fixed maturities
Fair value
Less than 12 months	120	202
12 months or longer	3	2
Total	123	204
Unrealized losses
Less than 12 months	3	4
12 months or longer	0	0
Total	3	4
No. of holdings	217	294
Indemnity | States & political subdivisions
Fair value
Less than 12 months	3	6
12 months or longer	0	2
Total	3	8
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	2	4
Indemnity | Corporate debt securities
Fair value
Less than 12 months	70	121
12 months or longer	3	0
Total	73	121
Unrealized losses
Less than 12 months	2	3
12 months or longer	0	0
Total	2	3
No. of holdings	185	250
Indemnity | Residential mortgage-backed securities
Fair value
Less than 12 months	3	6
12 months or longer	0	0
Total	3	6
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	3	4
Indemnity | Commercial mortgage-backed securities
Fair value
Less than 12 months	30	41
12 months or longer	0	0
Total	30	41
Unrealized losses
Less than 12 months	1	1
12 months or longer	0	0
Total	1	1
No. of holdings	20	24
Indemnity | Collateralized debt obligations
Fair value
Less than 12 months	13	21
12 months or longer	0	0
Total	13	21
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	6	9
Indemnity | Other debt securities
Fair value
Less than 12 months	1	7
12 months or longer	0	0
Total	1	7
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	3
Indemnity | Common stock
Fair value
Less than 12 months	13	0
12 months or longer	0	13
Total	13	13
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	1
Exchange
Fair value
Less than 12 months	849	1,134
12 months or longer	108	360
Total	957	1,494
Unrealized losses
Less than 12 months	23	32
12 months or longer	3	9
Total	26	41
No. of holdings	525	713
Exchange | Investment grade
Fair value
Less than 12 months	445	606
12 months or longer	82	253
Total	527	859
Unrealized losses
Less than 12 months	6	10
12 months or longer	1	5
Total	7	15
No. of holdings	136	172
Exchange | Non-investment grade
Fair value
Less than 12 months	357	442
12 months or longer	4	9
Total	361	451
Unrealized losses
Less than 12 months	17	19
12 months or longer	1	2
Total	18	21
No. of holdings	378	523
Exchange | Fixed maturities
Fair value
Less than 12 months	802	1,048
12 months or longer	86	262
Total	888	1,310
Unrealized losses
Less than 12 months	23	29
12 months or longer	2	7
Total	25	36
No. of holdings	514	695
Exchange | U.S. treasury
Fair value
Less than 12 months	0	1
12 months or longer	0	0
Total	0	1
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	2
Exchange | States & political subdivisions
Fair value
Less than 12 months	108	47
12 months or longer	5	47
Total	113	94
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	1
Total	1	1
No. of holdings	29	24
Exchange | Foreign government securities
Fair value
Less than 12 months	6
12 months or longer	0
Total	6
Unrealized losses
Less than 12 months	0
12 months or longer	0
Total	0
No. of holdings	6
Exchange | Corporate debt securities
Fair value
Less than 12 months	673	980
12 months or longer	56	181
Total	729	1,161
Unrealized losses
Less than 12 months	22	29
12 months or longer	2	5
Total	24	34
No. of holdings	468	656
Exchange | Residential mortgage-backed securities
Fair value
Less than 12 months	6	6
12 months or longer	17	27
Total	23	33
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	1
Total	0	1
No. of holdings	6	8
Exchange | Commercial mortgage-backed securities
Fair value
Less than 12 months	0	1
12 months or longer	1	0
Total	1	1
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	1	1
Exchange | Other debt securities
Fair value
Less than 12 months	9	13
12 months or longer	7	7
Total	16	20
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	0	0
No. of holdings	3	4
Exchange | Nonredeemable preferred stock
Fair value
Less than 12 months	47	86
12 months or longer	22	25
Total	69	111
Unrealized losses
Less than 12 months	0	3
12 months or longer	1	1
Total	1	4
No. of holdings	11	16
Exchange | Common stock
Fair value
Less than 12 months		0
12 months or longer		73
Total		73
Unrealized losses
Less than 12 months		0
12 months or longer		1
Total		$ 1
No. of holdings		2