Goodwill and Other Intangible Assets (Rollforward of Other Intangible Assets) (Details) - USD ($)			3 Months Ended	12 Months Ended
	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2018
Other Intangible Assets [Line Items]
Other intangible assets, gross							$ 354,000,000.0
Accumulated amortization							(184,600,000)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, beginning balance		$ 211,528,000		$ 211,528,000	$ 169,400,000
Additions from new business combinations				11,100,000	73,100,000
Intangible assets, gross (excluding goodwill), transfer in (out)				0
Measurement period adjustments				(200,000)	(6,900,000)
Intangible asset impairment, non-amortizing intangible assets					(3,300,000)	$ 0
Intangible asset impairment					(3,300,000)
Amortization expense				(38,900,000)	(23,000,000.0)
Currency translation adjustments				500,000	2,200,000
Other intangible assets, net, amortizing, ending balance	$ 149,500,000			149,500,000
Other intangible assets, net, ending balance	$ 184,043,000		$ 211,528,000	184,043,000	211,528,000	169,400,000
Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)	10 years
Customer Relationships and Backlog [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross							224,400,000
Accumulated amortization							(170,000,000.0)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, amortizing, beginning balance		95,300,000		95,300,000	54,400,000
Additions from new business combinations, amortizing intangible assets				11,000,000.0	67,700,000
Finite-lived intangible assets, transfer in (out)				0
Measurement period adjustments, amortizing intangible assets				(200,000)	(6,700,000)
Intangible asset impairment, amortizing intangible assets					0
Amortization expense				(26,700,000)	(20,200,000)
Currency translation adjustments, amortizing intangible assets				0	100,000
Other intangible assets, net, amortizing, ending balance	$ 79,400,000		95,300,000	79,400,000	95,300,000	54,400,000
Customer Relationships and Backlog [Member] | Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)	9 years
Other Amortizing Intangible Assets [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross							21,100,000
Accumulated amortization							(14,600,000)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, amortizing, beginning balance		8,800,000		8,800,000	6,500,000
Additions from new business combinations, amortizing intangible assets				100,000	5,200,000
Finite-lived intangible assets, transfer in (out)				0
Measurement period adjustments, amortizing intangible assets				0	(200,000)
Intangible asset impairment, amortizing intangible assets					0
Amortization expense				(2,000,000.0)	(2,800,000)
Currency translation adjustments, amortizing intangible assets				0	100,000
Other intangible assets, net, amortizing, ending balance	$ 6,900,000		8,800,000	6,900,000	8,800,000	6,500,000
Other Amortizing Intangible Assets [Member] | Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)	6 years
Pre-Qualifications [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross							0
Accumulated amortization							0
Other Intangible Assets [Roll Forward]
Other intangible assets, net, amortizing, beginning balance		$ 0		0	0
Additions from new business combinations, amortizing intangible assets				0	0
Finite-lived intangible assets, transfer in (out)				69,800,000
Measurement period adjustments, amortizing intangible assets				0	0
Intangible asset impairment, amortizing intangible assets					0
Amortization expense				(10,200,000)	0
Currency translation adjustments, amortizing intangible assets				3,600,000	0
Other intangible assets, net, amortizing, ending balance	$ 63,200,000		0	63,200,000	0	0
Pre-Qualifications [Member] | Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)	11 years	12 years
Trade Names [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing	$ 34,500,000	$ 34,500,000	34,500,000	34,500,000	34,500,000	34,500,000	34,500,000
Other Intangible Assets [Roll Forward]
Other intangible assets, non-amortizing, beginning balance		34,500,000		34,500,000	34,500,000
Additions from new business combinations, non-amortizing intangible assets				0	0
Indefinite-lived intangible assets, transfers in (out)				0
Measurement period adjustments, non-amortizing intangible assets				0	0
Intangible asset impairment, non-amortizing intangible assets					0
Currency translation adjustments, non-amortizing intangible assets				0	0
Other intangible assets, non-amortizing, ending balance	34,500,000		34,500,000	34,500,000	34,500,000	34,500,000
Pre-Qualifications [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing	0	72,900,000	72,900,000	0	72,900,000	74,000,000.0	$ 74,000,000.0
Other Intangible Assets [Roll Forward]
Other intangible assets, non-amortizing, beginning balance		$ 72,900,000		72,900,000	74,000,000.0
Additions from new business combinations, non-amortizing intangible assets				0	200,000
Indefinite-lived intangible assets, transfers in (out)				(69,800,000)
Measurement period adjustments, non-amortizing intangible assets				0	0
Intangible asset impairment, non-amortizing intangible assets			(3,300,000)		(3,300,000)
Currency translation adjustments, non-amortizing intangible assets				(3,100,000)	2,000,000.0
Other intangible assets, non-amortizing, ending balance	$ 0		$ 72,900,000	$ 0	$ 72,900,000	$ 74,000,000.0