Investments (Details 4) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investment income from portfolios
Investment income, net of expenses	$ 120	$ 115	$ 360	$ 335
Indemnity
Investment income from portfolios
Total investment income	5	4	14	12
Less: investment expenses	1	0	1	0
Investment income, net of expenses	4	4	13	12
Indemnity | Fixed maturities
Investment income from portfolios
Total investment income	4	4	12	10
Indemnity | Equity securities
Investment income from portfolios
Total investment income	1	0	1	1
Indemnity | Cash equivalents and other
Investment income from portfolios
Total investment income	0	0	1	1
Exchange
Investment income from portfolios
Total investment income	127	120	380	351
Less: investment expenses	11	9	33	28
Investment income, net of expenses	116	111	347	323
Exchange | Fixed maturities
Investment income from portfolios
Total investment income	97	90	287	261
Exchange | Equity securities
Investment income from portfolios
Total investment income	29	30	91	89
Exchange | Cash equivalents and other
Investment income from portfolios
Total investment income	$ 1	$ 0	$ 2	$ 1