Investments (Details 4) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Investment income from portfolios
Investment income, net of expenses	$ 109	$ 105	$ 316	$ 326
Indemnity
Investment income from portfolios
Total investment income	4	5	12	13
Less: investment expenses	0	1	1	1
Investment income, net of expenses	4	4	11	12
Indemnity | Fixed maturities
Investment income from portfolios
Total investment income	3	4	9	10
Indemnity | Equity securities
Investment income from portfolios
Total investment income	1	0	2	2
Indemnity | Cash equivalents and other
Investment income from portfolios
Total investment income	0	1	1	1
Exchange
Investment income from portfolios
Total investment income	113	110	330	340
Less: investment expenses	8	9	25	26
Investment income, net of expenses	105	101	305	314
Exchange | Fixed maturities
Investment income from portfolios
Total investment income	83	87	249	266
Exchange | Equity securities
Investment income from portfolios
Total investment income	29	23	80	72
Exchange | Cash equivalents and other
Investment income from portfolios
Total investment income	$ 1	$ 0	$ 1	$ 2