Goodwill and Other Intangible Assets (Rollforward of Other Intangible Assets) (Details) - USD ($) $ in Thousands			12 Months Ended
		Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013
Other Intangible Assets [Line Items]
Other intangible assets, gross carrying amount						$ 245,100
Accumulated amortization						(79,500)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, beginning balance			$ 250,373	$ 165,600
Additions from new business combinations, other intangible assets				116,300
Amortization expense			(28,400)	(25,100)	$ (21,200)
Currency translation adjustments, other intangible assets			(12,500)	(6,400)
Intangible asset impairment, other intangible assets			(10,100)
Other intangible assets, net, amortizing, ending balance		$ 91,200	91,200
Other intangible assets, net, ending balance		$ 199,379	199,379	250,373	165,600
Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)		11 years
Customer Relationships and Backlog [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross carrying amount						128,400
Accumulated amortization						(67,700)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, amortizing, beginning balance			109,500	60,700
Additions from new business combinations, amortizing intangible assets				73,400
Amortization expense			(26,500)	(23,200)
Currency translation adjustments, amortizing intangible assets			(2,200)	(1,400)
Intangible asset impairment, other intangible assets			0
Other intangible assets, net, amortizing, ending balance		$ 80,800	80,800	109,500	60,700
Customer Relationships and Backlog [Member] | Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)		11 years
Other Amortizing Intangible Assets [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross carrying amount	[1]					22,500
Accumulated amortization	[1]					(11,800)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, amortizing, beginning balance	[1]		12,800	10,700
Additions from new business combinations, amortizing intangible assets	[1]			4,200
Amortization expense	[1]		(1,900)	(1,900)
Currency translation adjustments, amortizing intangible assets	[1]		(500)	(200)
Intangible asset impairment, other intangible assets	[1]		0
Other intangible assets, net, amortizing, ending balance	[1]	$ 10,400	10,400	12,800	10,700
Other Amortizing Intangible Assets [Member] | Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)	[1]	11 years
Trade Names [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing, carrying amount		$ 34,800	34,800	34,800	34,800	34,800
Other Intangible Assets [Roll Forward]
Other intangible assets, non-amortizing, beginning balance			34,800	34,800
Additions from new business combinations, non-amortizing intangible assets				0
Currency translation adjustments, non-amortizing intangible assets			0	0
Intangible asset impairment, other intangible assets			0
Other intangible assets, non-amortizing, ending balance		34,800	34,800	34,800	34,800
Pre-Qualifications [Member]
Other Intangible Assets [Line Items]
Other intangible assets, non-amortizing, carrying amount		73,400	93,300	59,400	59,400	$ 59,400
Other Intangible Assets [Roll Forward]
Other intangible assets, non-amortizing, beginning balance			93,300	59,400
Additions from new business combinations, non-amortizing intangible assets				38,700
Currency translation adjustments, non-amortizing intangible assets			(9,800)	(4,800)
Intangible asset impairment, other intangible assets			(10,100)
Other intangible assets, non-amortizing, ending balance		$ 73,400	$ 73,400	$ 93,300	$ 59,400

[1] Consists principally of trade names and non-compete agreements.