Revisions in Estimates - Additional Information(Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2018
Change In Accounting Estimate [Line Items]
Impact from affirmative claim recovery estimate	$ 2.6	$ 1.8
Impact from estimated recovery of back charge claims	(0.4)	(0.3)
Minimum [Member] | Subsequent Event
Change In Accounting Estimate [Line Items]
Decrease on project revenue and profitability			$ 0.0
Maximum [Member] | Subsequent Event
Change In Accounting Estimate [Line Items]
Decrease on project revenue and profitability			$ 47.0
Revisions to Estimated Total Contract Costs [Member]
Change In Accounting Estimate [Line Items]
Impact from affirmative claim recovery estimate	2.1
Impact from estimated recovery of back charge claims	0.2
Estimated Costs Recorded in Prior Period [Member]
Change In Accounting Estimate [Line Items]
Impact from affirmative claim recovery estimate	0.5	(0.9)
Impact from estimated recovery of back charge claims	0.2
Revisions to Estimated Total Contract Costs [Member]
Change In Accounting Estimate [Line Items]
Impact from affirmative claim recovery estimate		2.7
Large Project Construction [Member]
Change In Accounting Estimate [Line Items]
Decrease on project revenue and profitability	4.9
Increase in net loss	1.6
Change in accounting estimate amount considered significant to individual project gross profit	1.0
Large Project Construction [Member] | Net Estimate Change [Member]
Change In Accounting Estimate [Line Items]
Increase (decrease) on project profitability	(7.9)	(13.0)
Large Project Construction [Member] | Contracts Accounted for under Percentage of Completion [Member] | Noncontrolling Interest [Member]
Change In Accounting Estimate [Line Items]
Increase (decrease) on project profitability	0.0	$ (1.6)
Construction Segment
Change In Accounting Estimate [Line Items]
Change in accounting estimate amount considered significant to individual project gross profit	$ 1.0