Commitments and Contingencies (Other Commitments and Contingencies) (Narrative) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member]
Loss Contingencies [Line Items]
Self insurance reserve	$ 85.8	$ 76.1
Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member] \| Other Long-Term Liabilities [Member]
Loss Contingencies [Line Items]
Self insurance reserve, non-current	55.2	47.5
Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member] \| Other Long-Term Assets [Member] \| Cash [Member]
Loss Contingencies [Line Items]
Cash collateral held by insurance carriers	1.5	1.3
Uninsured Risk [Member] \| Employee Group Medical Claims Policy [Member]
Loss Contingencies [Line Items]
Self insurance reserve	2.6	1.6
Performance and Payment Bonds [Member]
Loss Contingencies [Line Items]
Outstanding bonds, amount	72.9	539.3
Performance and Payment Bonds [Member] \| Estimate [Member]
Loss Contingencies [Line Items]
Bonded projects, costs to complete	9.5	36.0
Surety Bond [Member] \| Uninsured Risk [Member] \| Workers Compensation [Member]
Loss Contingencies [Line Items]
Outstanding bonds, amount	13.5	13.4
Credit Facility [Member]
Loss Contingencies [Line Items]
Letters of credit issued	314.3	292.8
Credit Facility [Member] \| Financial Guarantees [Member] \| Uninsured Risk [Member] \| Workers Compensation, General and Automobile Policies [Member]
Loss Contingencies [Line Items]
Letters of credit issued	$ 85.1	$ 83.2

Costs incurred and are directly related to generating contract revenues.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.2(e))
-URI http://asc.fasb.org/extlink&oid=63488584&loc=d3e20235-122688

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Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 460
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728

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Carrying amount (including both current and noncurrent portions) of accrued known and estimated losses incurred as of the balance sheet date for which no insurance coverage exists, and for which a claim has been made or is probable of being asserted, typically arising from workmen's compensation-type of incidents and personal injury to nonemployees from accidents on the entity's property.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.24)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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