Income Taxes (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income taxes
Deferred income tax (benefit) expense	$ 4	$ 198	$ 118
Provision for income taxes	257	519	280
Reconciliation of the provision for income taxes, with amounts determined by applying the statutory federal income tax rates to pre-tax income
Provision for income taxes	257	519	280
Indemnity
Income taxes
Current income tax expense	87	89	84
Deferred income tax (benefit) expense	(4)	(5)	(3)
Provision for income taxes	83	84	81
Reconciliation of the provision for income taxes, with amounts determined by applying the statutory federal income tax rates to pre-tax income
Income tax at statutory rates	88	86	84
Other, net	(5)	(2)	(3)
Provision for income taxes	83	84	81
Exchange
Income taxes
Current income tax expense	166	232	78
Deferred income tax (benefit) expense	8	203	121
Provision for income taxes	174	435	199
Reconciliation of the provision for income taxes, with amounts determined by applying the statutory federal income tax rates to pre-tax income
Income tax at statutory rates	202	462	230
Tax-exempt interest	(13)	(13)	(13)
Dividends received deduction	(15)	(14)	(14)
Other, net	0	0	(4)
Provision for income taxes	$ 174	$ 435	$ 199