Global Health Care Medical Claims Payable (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended	3 Months Ended	12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Accident and Health Insurance Segment [Member]	Dec. 31, 2012 Accident and Health Insurance Segment [Member]	Mar. 31, 2013 Completion Factors [Member] Accident and Health Insurance Segment [Member]	Dec. 31, 2012 Completion Factors [Member] Accident and Health Insurance Segment [Member]	Mar. 31, 2013 Medical Cost Trend [Member] Accident and Health Insurance Segment [Member]	Dec. 31, 2012 Medical Cost Trend [Member] Accident and Health Insurance Segment [Member]
Schedule Of Reported and Incurred but not Reported (IBNR) Medical Claims Payable (Details) [Abstract]
Incurred but not yet reported			$ 1,717	$ 1,541
Reported claims in process			190	243
Other medical expense payable			93	72
Medical claims payable			2,000	1,856
Schedule Of Medical Claims Payable Activity [Abstract]
Claims payable, beginning balance, gross			1,856	1,305
Less: Reinsurance and other amounts recoverable	6,256		242	249
Balance at January 1, net	4,062		1,614	1,056
Acquired net:			0	504
Incurred claims related to:
Current year			4,164	14,428
Prior years			(117)	(200)
Total incurred			4,047	14,228
Paid claims related to:
Current year			2,694	12,854
Prior years			1,162	1,320
Total paid			3,856	14,174
Balance at December 31, net	4,218		1,805	1,614
Add: Reinsurance and other amounts recoverable	7,514		195	242
Claims payable, ending balance, gross			2,000	1,856
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Abstract]
(Favorable) Unfavorable incurred claims related to prior years' claims payable			(117)	(200)	(47)	(91)	(70)	(109)
Incurred claims related to prior years' claims payable percentage			0.80%	2.20%	0.30%	1.00%	0.50%	1.20%
Impact Of Prior Year Development On Shareholders Net Income	$ 48	$ 41