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Commitments and Contingencies (Legal, Letters of Credit, Bonds, Self-Insurance) (Narrative) (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
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Commitments and Contingencies [Line Items] |  |
Letters of credit issued | $ 151.8 | $ 115.1
Self-Insurance [Member] | Workers' Compensation, General and Automobile Policies [Member] |  |
Commitments and Contingencies [Line Items] |  |
Self-insurance reserve | 129.6 | 123.4
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 | 86.1 | 87.3
Self-Insurance [Member] | Employee Group Medical Claims Policy [Member] |  |
Commitments and Contingencies [Line Items] |  |
Self-insurance reserve | 4.3 | 4.2
Performance and Payment Bonds [Member] |  |
Commitments and Contingencies [Line Items] |  |
Bonded projects, estimated costs to complete | 263.2 | 194.7
Performance and Payment Bonds [Member] | Subsidiaries [Member] |  |
Commitments and Contingencies [Line Items] |  |
Outstanding bonds, amount | 764.8 | 551.4
Financial Guarantees [Member] | Self-Insurance [Member] | Workers' Compensation, General and Automobile Policies [Member] |  |
Commitments and Contingencies [Line Items] |  |
Letters of credit issued | 59.3 | 64.0
Surety Bonds [Member] | Self-Insurance [Member] | Workers' Compensation [Member] |  |
Commitments and Contingencies [Line Items] |  |
Outstanding bonds, amount | $ 37.4 | $ 38.5

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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://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=121555522&loc=d3e12069-110248 + Details
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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://fasb.org/us-gaap/role/ref/legacyRef -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=120391452&loc=d3e13212-122682 + Details
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- Definition 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 No definition available. + Details
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