Long-Term Debt (Details) (USD $)	9 Months Ended
	Sep. 30, 2012
Line of Credit Facility [Line Items]
Line of Credit Facility, Expiration Date	Oct. 11, 2016
Maximum borrowing capacity	$ 2,000,000,000
Eurodollar rate at period end (in hundredths)	1.09%
Base rate at period end (in hundredths)	3.25%
Debt Instrument Issuance [Abstract]
Proceeds from Issuance of Senior Long-term Debt	1,234,000,000
Debt Instrument Issuance Face Amount	1,250,000,000
Debt Instrument Offering Date	Sep. 10, 2012
Debt Instrument Issuance Interest Rate	2.625%
Capital Lease [Abstract]
Capital Lease Term (in years)	10
Capital Lease Optional Additional Term (in years)	5
Capital Lease Obligations Incurred	66,000,000
Capital Lease Obligations, Noncurrent	59,000,000
Capital Lease Obligations, Current	7,000,000
Capital Leases, Future Minimum Payments Due	76,000,000
Uncommitted Credit Facility [Member]
Line of Credit Facility [Line Items]
Weighted average interest rate (in hundredths)	0.70%
Average Borrowings Outstanding	55,000
Commercial Paper [Member]
Line of Credit Facility [Line Items]
Weighted average interest rate (in hundredths)	0.45%
Average Borrowings Outstanding	$ 315,000,000