Revisions in Estimates - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Change In Accounting Estimate [Line Items]
Decrease on project revenue and profitability			$ 4.9
Increase in net loss			1.6
Impact from affirmative claim recovery estimate	$ 1.2	$ 11.5	6.1	$ 25.5
Impact from estimated recovery of back charge claims	(1.6)	0.6	(3.6)	3.6
Change in accounting estimate amount considered significant to individual project gross profit			5.0	5.0
Minimum [Member]
Change In Accounting Estimate [Line Items]
Decrease on project revenue and profitability			0.0
Maximum [Member]
Change In Accounting Estimate [Line Items]
Decrease on project revenue and profitability			45.0
Revisions to Estimated Total Contract Costs [Member]
Change In Accounting Estimate [Line Items]
Impact from affirmative claim recovery estimate	0.2		8.7
Impact from estimated recovery of back charge claims	1.4	0.6	2.5	2.0
Estimated Costs Recorded in Prior Period [Member]
Change In Accounting Estimate [Line Items]
Impact from affirmative claim recovery estimate	1.0	0.5	(2.6)	0.4
Impact from estimated recovery of back charge claims	(0.2)		(1.1)	(1.6)
Revisions to Estimated Total Contract Costs [Member]
Change In Accounting Estimate [Line Items]
Impact from affirmative claim recovery estimate		11.0		25.1
Net Estimate Change [Member]
Change In Accounting Estimate [Line Items]
Increase (decrease) on project profitability	(19.3)	(12.7)	(57.8)	(56.8)
Net Estimate Change [Member] | Specialty [Member]
Change In Accounting Estimate [Line Items]
Increase (decrease) on project profitability				(5.9)
Contracts Accounted for under Percentage of Completion [Member] | Noncontrolling Interest [Member]
Change In Accounting Estimate [Line Items]
Increase (decrease) on project profitability	$ 0.0	$ 0.0	$ 0.0	$ (2.1)