Indebtedness (Commercial Paper Narrative) (Details) (USD $)	3 Months Ended
	Jun. 30, 2013	Mar. 31, 2013
Debt Instrument [Line Items]
Short-term debt	$ 49,000,000	$ 0
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Revolving line of credit, maximum borrowing capacity	750,000,000
Commercial paper [Member]
Debt Instrument [Line Items]
Revolving line of credit, maximum borrowing capacity	750,000,000
Short-term debt, terms	maturities that may vary, but will generally not exceed 90 days from the date of issue
Short-term debt	$ 49,000,000	$ 0
Debt Instrument, Interest Rate, Effective Percentage	0.30%
Maximum [Member] | Commercial paper [Member]
Debt Instrument [Line Items]
Short term debt maturity period	90 days