Investments (Details 4) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Investment income from portfolios
Investment income, net of expenses	$ 127	$ 111	$ 240	$ 220
Indemnity
Investment income from portfolios
Total investment income	5	4	9	8
Less: investment expenses	0	0	0	0
Investment income, net of expenses	5	4	9	8
Indemnity | Fixed maturities
Investment income from portfolios
Total investment income	4	3	8	6
Indemnity | Equity securities
Investment income from portfolios
Total investment income	0	0	0	1
Indemnity | Cash equivalents and other
Investment income from portfolios
Total investment income	1	1	1	1
Exchange
Investment income from portfolios
Total investment income	132	116	253	231
Less: investment expenses	10	9	22	19
Investment income, net of expenses	122	107	231	212
Exchange | Fixed maturities
Investment income from portfolios
Total investment income	96	85	190	171
Exchange | Equity securities
Investment income from portfolios
Total investment income	36	30	62	59
Exchange | Cash equivalents and other
Investment income from portfolios
Total investment income	$ 0	$ 1	$ 1	$ 1