Goodwill and Other Intangible Assets (Rollforward of Other Intangible Assets) (Details) - USD ($) $ in Thousands		6 Months Ended
	Jan. 01, 2020	Jun. 30, 2020	Dec. 31, 2019
Other Intangible Assets [Line Items]
Other intangible assets, gross			$ 420,200
Accumulated amortization			(208,700)
Other Intangible Assets [Rollforward]
Other intangible assets, net, beginning balance	$ 211,528	$ 211,528
Additions from new business combinations		9,800
Transfers in (out)		0
Measurement period adjustments		(200)
Currency translation adjustments		(1,700)
Amortization expense		(17,200)
Other intangible assets, net, ending balance		202,165
Customer Relationships and Backlog [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross			286,500
Accumulated amortization			(191,200)
Other Intangible Assets [Rollforward]
Other intangible assets, net, amortizing, beginning balance	95,300	95,300
Additions from new business combinations, amortizing intangible assets		9,700
Transfers in (out), amortizing intangible assets		0
Measurement period adjustments, amortizing intangible assets		(200)
Currency translation adjustments, amortizing intangible assets		100
Amortization expense		(12,200)
Other intangible assets, net, amortizing, ending balance		92,700
Pre-Qualifications [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross			0
Accumulated amortization			0
Other Intangible Assets [Rollforward]
Other intangible assets, net, amortizing, beginning balance	$ 0	0
Additions from new business combinations, amortizing intangible assets		0
Transfers in (out), amortizing intangible assets		69,800
Measurement period adjustments, amortizing intangible assets		0
Currency translation adjustments, amortizing intangible assets		1,300
Amortization expense		(4,000)
Other intangible assets, net, amortizing, ending balance		67,100
Pre-Qualifications [Member] | Weighted Average [Member]
Other Intangible Assets [Rollforward]
Remaining amortization period (in years)	12 years
Other Amortizing Intangible Assets [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross			26,300
Accumulated amortization			(17,500)
Other Intangible Assets [Rollforward]
Other intangible assets, net, amortizing, beginning balance	$ 8,800	8,800
Additions from new business combinations, amortizing intangible assets		100
Transfers in (out), amortizing intangible assets		0
Measurement period adjustments, amortizing intangible assets		0
Currency translation adjustments, amortizing intangible assets		0
Amortization expense		(1,000)
Other intangible assets, net, amortizing, ending balance		7,900
Trade Names [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing	34,500	34,500	34,500
Other Intangible Assets [Rollforward]
Other intangible assets, non-amortizing, beginning balance	34,500	34,500
Additions from new business combinations, non-amortizing intangible assets		0
Transfers in (out), non-amortizing intangible assets		0
Measurement period adjustments, non-amortizing intangible assets		0
Currency translation adjustments, non-amortizing intangible assets		0
Other intangible assets, non-amortizing, ending balance		34,500
Pre-Qualifications [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing	72,900	0	$ 72,900
Other Intangible Assets [Rollforward]
Other intangible assets, non-amortizing, beginning balance	$ 72,900	72,900
Additions from new business combinations, non-amortizing intangible assets		0
Transfers in (out), non-amortizing intangible assets		(69,800)
Measurement period adjustments, non-amortizing intangible assets		0
Currency translation adjustments, non-amortizing intangible assets		(3,100)
Other intangible assets, non-amortizing, ending balance		$ 0