Commitments and Contingencies (Other Commitments and Contingencies) (Narrative) (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Self-Insurance [Member] \| Workers' Compensation, General and Automobile Policies [Member]
Commitments and Contingencies [Line Items]
Self-insurance reserve	$ 111.8	$ 106.2
Self-Insurance [Member] \| Workers' Compensation, General and Automobile Policies [Member] \| Other Long-Term Liabilities [Member]
Commitments and Contingencies [Line Items]
Self-insurance reserve, non-current	76.6	72.2
Self-Insurance [Member] \| Workers' Compensation, General and Automobile Policies [Member] \| Other Long-Term Assets [Member] \| Cash [Member]
Commitments and Contingencies [Line Items]
Cash collateral held by insurance carriers	1.6	1.6
Self-Insurance [Member] \| Employee Group Medical Claims Policies [Member]
Commitments and Contingencies [Line Items]
Self-insurance reserve	2.4	2.6
Performance and Payment Bonds [Member] \| Estimate [Member]
Commitments and Contingencies [Line Items]
Bonded projects, costs to complete	127.7	46.0
Performance and Payment Bonds [Member] \| Subsidiaries [Member]
Commitments and Contingencies [Line Items]
Outstanding bonds, amount	129.6	119.7
Surety Bond [Member] \| Self-Insurance [Member] \| Workers' Compensation [Member]
Commitments and Contingencies [Line Items]
Outstanding bonds, amount	15.2	15.2
Credit Facility [Member]
Commitments and Contingencies [Line Items]
Letters of credit issued	131.7	157.1
Credit Facility [Member] \| Financial Guarantees [Member] \| Self-Insurance [Member] \| Workers' Compensation, General and Automobile Policies [Member]
Commitments and Contingencies [Line Items]
Letters of credit issued	$ 88.9	$ 88.9

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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- Definition

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=82913245&loc=d3e12069-110248

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- Definition

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

+ References

No definition available.

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+ References

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The fair value, as of the date of each statement of financial position presented, of other assets which are owned but transferred to serve as collateral for the payment of the related debt obligation, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

+ 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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- Definition

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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Carrying amount 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 that are expected to be paid after one year (or the normal operating cycle, if longer).

+ References

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