Investments (Details 12) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Investment Holdings
Limited partnership interests	$ 4,309		$ 4,309		$ 4,967
Total other-than-temporary impairment losses	44	55	124	82
Tax credit funds	592		592
Other details of unrealized loss
Unrealized losses related to securities with unrealized loss position less than 20% of cost or amortized cost	136		136
Unrealized losses related to securities with unrealized loss position greater than or equal to 20% of cost or amortized cost	42		42
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	80		80
Unrealized losses related to securities with unrealized loss position greater than or equal to 20% of cost or amortized cost	25		25
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 cost or amortized cost	17		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	12		12
Equity-method limited partnerships
Investment Holdings
Limited partnership interests	3,150		3,150		3,520
Total other-than-temporary impairment losses	0	0	0	0
Cost-method limited partnership interests
Investment Holdings
Limited partnership interests	1,160		1,160		1,440
Total other-than-temporary impairment losses	$ 6	$ 8	$ 19	$ 8