Debt (Senior Secured Credit Facility) (Narrative) (Details) - Credit Facility [Member] - USD ($)			3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2015
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,250,000,000		$ 1,250,000,000
Line of credit facility, maturity date			Oct. 29, 2018
Line of credit facility, deferred financing costs, net of accumulated amortization	6,400,000	$ 6,900,000	$ 6,400,000
Line of credit facility, letters of credit issued	$ 153,200,000	$ 153,600,000	$ 153,200,000
Line of credit facility, unused facility fee (percentage)	0.35%	0.35%
Line of credit facility, collateral			The Credit Facility is guaranteed by certain subsidiaries of the Company (the “Guarantor Subsidiaries”), and the obligations under the Credit Facility are secured by substantially all of the Company’s and the Guarantor Subsidiaries’ respective assets, subject to certain exceptions.
Maximum [Member]
Debt Instrument [Line Items]
Line of credit facility, revolving loan sublimit, Canadian dollars or Mexican pesos	$ 200,000,000		$ 200,000,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	1,000,000,000		1,000,000,000
Line of credit facility, remaining borrowing capacity	$ 543,200,000	$ 563,700,000	$ 543,200,000
Revolving Credit Facility [Member] | Weighted Average [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	2.52%	2.18%	2.52%
Term Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000		$ 250,000,000
Line of credit facility, maturity date			Nov. 21, 2019
Line of credit facility, term loan, frequency of payments			quarterly
Line of credit facility, term loan, date of first required payment			Mar. 31, 2016
Line of credit facility, interest rate (percentage)	1.92%	1.92%	1.92%
Term Loan [Member] | Plan [Member]
Debt Instrument [Line Items]
Line of credit facility, term loan, amount of quarterly principal installment payments			$ 3,100,000
Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of credit facility, revolving loan sublimit	$ 75,000,000		75,000,000
Letters of Credit [Member]
Debt Instrument [Line Items]
Line of credit facility, capacity available for letters of credit	$ 296,800,000	$ 296,400,000	$ 296,800,000
Letters of Credit [Member] | Performance Guarantees [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	0.875%	0.875%	0.875%
Letters of Credit [Member] | Financial Standby [Member]
Debt Instrument [Line Items]
Line of credit facility, interest rate (percentage)	1.75%	1.75%	1.75%
Letters of Credit [Member] | Maximum [Member]
Debt Instrument [Line Items]
Line of credit facility, capacity available for letters of credit	$ 450,000,000		$ 450,000,000
Line of credit facility, capacity available for letters of credit sublimit, Canadian dollars or Mexican pesos	100,000,000		100,000,000
Option to Increase Revolving Commitments and/or Establish Additional Term Loan Tranches [Member] | Plan [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000		$ 250,000,000