Long-Term Debt (Credit Facility End of Period Disclosures Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2013 item
Credit Facility, Name [Member] | Credit Facility, Type of Debt [Member]
Debt Instrument [Line Items]
Minimum Number of Additional Tranches Available in Future	1
Aggregate Principal Amount of Each Tranche Available in Future	$ 1,000,000,000
Debt, Weighted Average Interest Rate	4.30%
Credit Facility, Revolving Credit Loans [Member] | Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Remaining Borrowing Capacity	750,000,000
Letters of Credit Outstanding, Amount	$ 37,800,000