Debt Debt, Textuals (Details) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended
	Jul. 02, 2013	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Jun. 30, 2013	May 28, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		5.72%		5.72%				6.28%
Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate		92.00%		92.00%				87.00%
Financing Commitment							$ 1,825,000,000
Line of Credit Facility, Maximum Borrowing Capacity		500,000,000		500,000,000
Consent Solitication Fee		0.25%
Long-term Line of Credit							600,000,000
Pending Divestiture Proceeds	200,000,000
Leverage Ratio with payment terms	375.00%
Bridge Loan							725,000,000
Credit Facility, Maximum Borrowing Capacity	1,100,000,000
Letters of Credit, Maximum Borrowing Capacity		175,000,000		175,000,000
Line of Credit Facility, Amount Outstanding		0		0		86,600,000		86,600,000
Letters of Credit Outstanding, Amount		31,800,000		31,800,000
Repayments of Debt and Capital Lease Obligations				19,700,000
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage		0.25%
Line of Credit Facility, Remaining Borrowing Capacity		468,200,000		468,200,000
Repayments of Long-term Capital Lease Obligations				19,585,000	19,303,000
Repayments of Debt				100,000
Gains (Losses) on Extinguishment of Debt		0	0	468,000	0
Capital Lease Obligations Incurred				34,000,000	51,000,000
Proceeds from Issuance of Long-term Debt	425,000,000
Debt Instrument, Interest Rate, Stated Percentage	5.375%
Unsecured Debt [Member] | February 2013 [Member]
Debt Instrument [Line Items]
Senior Notes		0		0				4,757,000
Unsecured Debt [Member] | April 2015 [Member]
Debt Instrument [Line Items]
Senior Notes		136,465,000		136,465,000				136,465,000
Unsecured Debt [Member] | April 2016 [Member]
Debt Instrument [Line Items]
Senior Notes		197,377,000		197,377,000				197,377,000
Unsecured Debt [Member] | June 2017 [Member]
Debt Instrument [Line Items]
Senior Notes		295,000,000		295,000,000				295,000,000
Unsecured Debt [Member] | October 2018 [Member]
Debt Instrument [Line Items]
Senior Notes		250,000,000		250,000,000				250,000,000
Unsecured Debt [Member] | May 2019 [Member]
Debt Instrument [Line Items]
Senior Notes		250,000,000		250,000,000				250,000,000
Unsecured Debt [Member] | November 2020 [Member]
Debt Instrument [Line Items]
Senior Notes		200,000,000		200,000,000				200,000,000
Unsecured Debt [Member] | November 2021 [Member]
Debt Instrument [Line Items]
Senior Notes		150,000,000		150,000,000				150,000,000
Unsecured Debt [Member] | April 2027 [Member]
Debt Instrument [Line Items]
Senior Notes		$ 200,000,000		$ 200,000,000				$ 200,000,000