Investments (Details 11) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position less than 20% of amortized cost or cost	$ 191
Unrealized losses related to securities with unrealized loss position greater than or equal to 20% of amortized cost or cost	54
Limited partnerships
Limited partnership interests	2,121		2,064
Write-downs of limited partnership	8	1
Equity method limited partnerships
Limited partnerships
Limited partnership interests	1,520		1,460
Write-downs of limited partnership	0	0
Cost method limited partnership interests
Limited partnerships
Limited partnership interests	603		605
Write-downs of limited partnership	7	0
Investment grade fixed income securities
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position less than 20% of amortized cost or cost	154
Unrealized losses related to securities with unrealized loss position greater than or equal to 20% of amortized cost or cost	37
Below investment grade fixed income securities
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position greater than or equal to 20% of amortized cost or cost	17
Unrealized losses related to securities with unrealized loss position greater than 20% of cost or amortized cost, unrealized loss position of 12 or more consecutive months	$ 9