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Commitments and Contingencies (Other Commitments and Contingencies) (Narrative) (Details) - USD ($)			1 Months Ended	6 Months Ended
	Jun. 30, 2015	Dec. 31, 2014	Aug. 12, 2015	Jun. 30, 2015
Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member]
Commitments and Contingencies [Line Items]
Self insurance reserve	$ 70,800,000	$ 70,300,000		$ 70,800,000
Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member] \| Other Long-Term Liabilities [Member]
Commitments and Contingencies [Line Items]
Self insurance reserve, non-current	41,600,000	39,600,000		41,600,000
Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member] \| Other Long-Term Assets [Member]
Commitments and Contingencies [Line Items]
Cash collateral held by insurance carriers	1,400,000	1,200,000		1,400,000
Uninsured Risk [Member] \| Employee Group Medical Claims Policies [Member]
Commitments and Contingencies [Line Items]
Self insurance reserve	3,700,000	4,400,000		3,700,000
Canadian Dollars [Member] \| Investee [Member] \| Financial Support [Member]
Commitments and Contingencies [Line Items]
Financing commitments, amounts paid				13,900,000
Unconsolidated affiliates, outstanding commitments	0	0		0
Canadian Dollars [Member] \| Subsequent Event [Member] \| Investee [Member] \| Financial Support [Member]
Commitments and Contingencies [Line Items]
Financing commitments, amounts paid			$ 2,400,000
Performance and Payment Bonds [Member]
Commitments and Contingencies [Line Items]
Outstanding bonds, amount	653,100,000	748,300,000		653,100,000
Performance and Payment Bonds [Member] \| Estimate [Member]
Commitments and Contingencies [Line Items]
Bonded projects, costs to complete	24,400,000	60,100,000
Surety Bond [Member] \| Uninsured Risk [Member] \| Workers Compensation [Member]
Commitments and Contingencies [Line Items]
Outstanding bonds, amount	13,000,000	13,000,000		13,000,000
Credit Facility [Member]
Commitments and Contingencies [Line Items]
Letters of credit issued	175,800,000	153,600,000		175,800,000
Credit Facility [Member] \| Financial Guarantees [Member] \| Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member]
Commitments and Contingencies [Line Items]
Letters of credit issued	$ 75,000,000	$ 75,000,000		$ 75,000,000