Accounting Policies (Details) (USD $) In Billions, unless otherwise specified	9 Months Ended
	Sep. 30, 2011 M manager platform case segment state Y store
Fair Value of Financial Instruments
Minimum initial maturities of short-term investments (in months)	3
Carrying amount of long-term debt	$ 10.2
Estimated fair value of long-term debt	$ 11.5