Commitments and Contingencies (Other Commitments and Contingencies) (Narrative) (Details) - USD ($)	Dec. 31, 2014	Dec. 31, 2013
Uninsured Risk [Member] | Workers Compensation, General and Automobile Policies [Member]
Loss Contingencies [Line Items]
Self insurance reserve	$ 70,300,000	$ 50,800,000
Uninsured Risk [Member] | Workers Compensation, General and Automobile Policies [Member] | Other Long-Term Liabilities [Member]
Loss Contingencies [Line Items]
Self insurance reserve, non-current	39,600,000	31,300,000
Uninsured Risk [Member] | Workers Compensation, General and Automobile Policies [Member] | Other Long-Term Assets [Member]
Loss Contingencies [Line Items]
Cash collateral held by insurance carriers	1,200,000	1,400,000
Uninsured Risk [Member] | Employee Group Medical Claims Policy [Member]
Loss Contingencies [Line Items]
Self insurance reserve	4,400,000	2,100,000
Unconsolidated Affiliates [Member] | Financial Support [Member]
Loss Contingencies [Line Items]
Unconsolidated affiliates, outstanding commitments	0
Performance and Payment Bonds [Member]
Loss Contingencies [Line Items]
Outstanding bonds, amount	748,300,000	1,100,000,000
Performance and Payment Bonds [Member] | Estimate [Member]
Loss Contingencies [Line Items]
Bonded projects, costs to complete	60,100,000	297,100,000
Surety Bond [Member] | Uninsured Risk [Member] | Workers Compensation [Member]
Loss Contingencies [Line Items]
Outstanding bonds, amount	13,000,000	10,900,000
Credit Facility [Member]
Loss Contingencies [Line Items]
Letters of credit issued	153,600,000	134,800,000
Credit Facility [Member] | Financial Guarantees [Member] | Uninsured Risk [Member] | Workers Compensation, General and Automobile Policies [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 75,000,000	$ 57,400,000