Long-Term Debt - Credit Facility - End of Period Disclosures (Details) (USD $)	6 Months Ended
	Jun. 30, 2012
Debt Instrument [Line Items]
Line of Credit Facility, Amount Outstanding	$ 5,000,000
Credit Facility, Name [Member] | Credit Facility, Type of Debt [Member]
Debt Instrument [Line Items]
Minimum Number of Tranches Available in Future	1
Aggregate Principal Amount of Each Tranche Available in Future	1,000,000,000
Debt, Weighted Average Interest Rate	3.50%
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	$ 37,700,000