Debt (Narrative) (Details) (USD $) In Billions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 yr
Debt Instrument [Line Items]
Notional amounts of interest rate swaps	1.6
Seven-Year 4.45% U.S. Dollar Notes Due 2016 [Member]
Debt Instrument [Line Items]
Debt instrument term, in years	7
Debt instrument maturity year	2016
Debt instrument, stated interest rate	4.45%
Effective interest rate	3.336%
Five-Year 1.875% U.S. Dollar Notes Due 2016 [Member]
Debt Instrument [Line Items]
Debt instrument term, in years	5
Debt instrument maturity year	2016
Debt instrument, stated interest rate	1.875%
Effective interest rate	1.214%
Ten-Year 4.15% U.S. Dollar Notes Due 2019 [Member]
Debt Instrument [Line Items]
Debt instrument term, in years	10
Debt instrument maturity year	2019
Debt instrument, stated interest rate	4.15%
Effective interest rate	2.786%
364-Day Term Loan Agreement [Member]
Debt Instrument [Line Items]
Number of days until note maturity	364
Credit facility, maximum borrowing capacity	1