Investments (Details 11) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position less than 20% of cost or amortized cost	$ 750		$ 750
Unrealized losses related to securities with unrealized loss position greater than 20% of cost or amortized cost	924		924
Percentage of amortized cost or cost (as a percent)	20.00%		20.00%
Limited partnership impairment
Limited partnership interests	4,400		4,400		3,816
Equity-method limited partnership interests
Limited partnership impairment
Limited partnership interests	2,990		2,990		2,470
Write-downs of limited partnership		1		1
Cost-method limited partnership interests
Limited partnership impairment
Limited partnership interests	1,410		1,410		1,350
Write-downs of limited partnership	1	7	2	31
Investment grade fixed income securities
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position less than 20% of cost or amortized cost	532		532
Unrealized losses related to securities with unrealized loss position greater than 20% of cost or amortized cost	231		231
Below investment grade fixed income securities
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position greater than 20% of cost or amortized cost	660		660
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	542		542
Equity securities
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position greater than 20% of cost or amortized cost	$ 33		$ 33