Employee Retirement Plans - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Retirement Benefits [Abstract]
Actual employer contributions to defined benefit plans	$ 0.7
Expected full year contributions by the employer to defined benefit plans	18.4
Contributions to multiemployer plan	0.6	$ 0.6
Expected full year contributions by the employer to the multiemployer plan	$ 2.5

Multiemployer Plan, Expected Contributions in Current Fiscal Year

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- References

No definition available.

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- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
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Amount of contributions received and expected to be received by defined benefit plan from employer in current fiscal year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
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-Paragraph 6
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- Definition

Amount of contributions made to multiemployer plan by employer.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 80
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