Investments (Details 3) $ in Millions	Sep. 30, 2015 USD ($) Holdings	Dec. 31, 2014 USD ($) Holdings
Indemnity
Fair value
Less than 12 months	$ 199	$ 202
12 months or longer	48	15
Total	247	217
Unrealized losses
Less than 12 months	2	4
12 months or longer	4	0
Total	$ 6	$ 4
No. of holdings | Holdings	345	295
Indemnity | Investment grade
Fair value
Less than 12 months	$ 131	$ 146
12 months or longer	35	2
Total	166	148
Unrealized losses
Less than 12 months	0	1
12 months or longer	1	0
Total	$ 1	$ 1
No. of holdings | Holdings	80	58
Indemnity | Non-investment grade
Fair value
Less than 12 months	$ 52	$ 56
12 months or longer	13	0
Total	65	56
Unrealized losses
Less than 12 months	1	3
12 months or longer	3	0
Total	$ 4	$ 3
No. of holdings | Holdings	262	236
Indemnity | Fixed maturities
Fair value
Less than 12 months	$ 183	$ 202
12 months or longer	48	2
Total	231	204
Unrealized losses
Less than 12 months	1	4
12 months or longer	4	0
Total	$ 5	$ 4
No. of holdings | Holdings	342	294
Indemnity | States & political subdivisions
Fair value
Less than 12 months	$ 4	$ 6
12 months or longer	0	2
Total	4	8
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0
No. of holdings | Holdings	2	4
Indemnity | Corporate debt securities
Fair value
Less than 12 months	$ 134	$ 121
12 months or longer	17	0
Total	151	121
Unrealized losses
Less than 12 months	1	3
12 months or longer	3	0
Total	$ 4	$ 3
No. of holdings | Holdings	292	250
Indemnity | Residential mortgage-backed securities
Fair value
Less than 12 months	$ 2	$ 6
12 months or longer	1	0
Total	3	6
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0
No. of holdings | Holdings	4	4
Indemnity | Commercial mortgage-backed securities
Fair value
Less than 12 months	$ 16	$ 41
12 months or longer	23	0
Total	39	41
Unrealized losses
Less than 12 months	0	1
12 months or longer	1	0
Total	$ 1	$ 1
No. of holdings | Holdings	26	24
Indemnity | Collateralized debt obligations
Fair value
Less than 12 months	$ 22	$ 21
12 months or longer	7	0
Total	29	21
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0
No. of holdings | Holdings	15	9
Indemnity | Other debt securities
Fair value
Less than 12 months	$ 5	$ 7
12 months or longer	0	0
Total	5	7
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0
No. of holdings | Holdings	3	3
Indemnity | Nonredeemable preferred stock
Fair value
Less than 12 months	$ 3
12 months or longer	0
Total	3
Unrealized losses
Less than 12 months	0
12 months or longer	0
Total	$ 0
No. of holdings | Holdings	2
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	1	0
12 months or longer	0	0
Total	$ 1	$ 0
No. of holdings | Holdings	1	1
Exchange
Fair value
Less than 12 months	$ 2,286	$ 1,134
12 months or longer	200	360
Total	2,486	1,494
Unrealized losses
Less than 12 months	95	32
12 months or longer	24	9
Total	$ 119	$ 41
No. of holdings | Holdings	1,096	713
Exchange | Investment grade
Fair value
Less than 12 months	$ 1,521	$ 606
12 months or longer	109	253
Total	1,630	859
Unrealized losses
Less than 12 months	62	10
12 months or longer	9	5
Total	$ 71	$ 15
No. of holdings | Holdings	434	172
Exchange | Non-investment grade
Fair value
Less than 12 months	$ 588	$ 442
12 months or longer	67	9
Total	655	451
Unrealized losses
Less than 12 months	28	19
12 months or longer	14	2
Total	$ 42	$ 21
No. of holdings | Holdings	632	523
Exchange | Fixed maturities
Fair value
Less than 12 months	$ 2,109	$ 1,048
12 months or longer	176	262
Total	2,285	1,310
Unrealized losses
Less than 12 months	90	29
12 months or longer	23	7
Total	$ 113	$ 36
No. of holdings | Holdings	1,066	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 | Holdings	1	2
Exchange | States & political subdivisions
Fair value
Less than 12 months	$ 75	$ 47
12 months or longer	5	47
Total	80	94
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	1
Total	$ 1	$ 1
No. of holdings | Holdings	20	24
Exchange | Foreign government securities
Fair value
Less than 12 months	$ 77
12 months or longer	0
Total	77
Unrealized losses
Less than 12 months	5
12 months or longer	0
Total	$ 5
No. of holdings | Holdings	51
Exchange | Corporate debt securities
Fair value
Less than 12 months	$ 1,951	$ 980
12 months or longer	151	181
Total	2,102	1,161
Unrealized losses
Less than 12 months	84	29
12 months or longer	23	5
Total	$ 107	$ 34
No. of holdings | Holdings	987	656
Exchange | Residential mortgage-backed securities
Fair value
Less than 12 months	$ 0	$ 6
12 months or longer	13	27
Total	13	33
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	1
Total	$ 0	$ 1
No. of holdings | Holdings	3	8
Exchange | Commercial mortgage-backed securities
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 | Holdings		1
Exchange | Other debt securities
Fair value
Less than 12 months	$ 6	$ 13
12 months or longer	7	7
Total	13	20
Unrealized losses
Less than 12 months	0	0
12 months or longer	0	0
Total	$ 0	$ 0
No. of holdings | Holdings	4	4
Exchange | Nonredeemable preferred stock
Fair value
Less than 12 months	$ 146	$ 86
12 months or longer	24	25
Total	170	111
Unrealized losses
Less than 12 months	4	3
12 months or longer	1	1
Total	$ 5	$ 4
No. of holdings | Holdings	29	16
Exchange | Common stock
Fair value
Less than 12 months	$ 31	$ 0
12 months or longer	0	73
Total	31	73
Unrealized losses
Less than 12 months	1	0
12 months or longer	0	1
Total	$ 1	$ 1
No. of holdings | Holdings	1	2