Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Income Taxes [Abstract]
Income tax expense	$ 59	$ (60)	$ 184	$ 94	$ 46
Effective tax rate	45.40%		33.50%	19.70%
Increase in effective tax rate from transformation cost	4.10%		0.80%
Deferred tax valuation adjustments	11.60%		2.80%
Increase in effective tax rate due to impact of the Medicare Part D subsidy reversal				1.50%
Reduced effective tax rate related to the effective settlement of a tax examination	3.70%			1.00%
Benefit from reversal of valuation allowances on certain loss carryforwards		27
Unrecognized tax benefits	161		161		192
Amount of unrecognized tax benefits that would affect the effective tax rate	80		80		90
Potential decrease in unrecognized tax benefits related to amortization of temporary tax differences	8		8
Deferred tax assets	1,044		1,044		769
Increase in deferred tax assets			$ 275