Investments (details) - Derivatives (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014		Dec. 31, 2014
Derivatives
Net realized investment gains (losses)	$ 10	[1]	$ 1	[1]
Futures [Member] | U.S. Treasury notes contracts [Member]
Derivatives
Notional value of open contracts	400				350
Net realized investment gains (losses)	$ (10)		$ 1

[1] Total other-than-temporary impairment (OTTI) losses were $(4) million and $(7) million for the three months ended March 31, 2015 and 2014, respectively. Of total OTTI, credit losses of $(3) million and $(9) million for the three months ended March 31, 2015 and 2014, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $(1) million and $2 million for the three months ended March 31, 2015 and 2014, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income.