Goodwill and Other Intangible Assets (Rollforward of Other Intangible Assets) (Details) - USD ($) $ in Thousands			12 Months Ended
		Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Intangible Assets [Line Items]
Other intangible assets, gross carrying amount					$ 195,500
Accumulated amortization					(58,500)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, beginning balance			$ 165,606	$ 137,000
Additions from new business combinations, other intangible assets			116,300	51,900
Amortization expense			(25,100)	(21,200)	(12,200)
Currency translation adjustments, other intangible assets			(6,400)	(2,100)
Other intangible assets, net, amortizing, ending balance		$ 122,300	122,300
Other intangible assets, net, ending balance		$ 250,373	250,373	165,606	137,000
Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)		13 years
Customer Relationships and Backlog [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross carrying amount					109,600
Accumulated amortization					(48,300)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, amortizing, beginning balance			60,700	61,300
Additions from new business combinations, amortizing intangible assets			73,400	19,500
Amortization expense			(23,200)	(19,600)
Currency translation adjustments, amortizing intangible assets			(1,400)	(500)
Other intangible assets, net, amortizing, ending balance		$ 109,500	109,500	60,700	61,300
Customer Relationships and Backlog [Member] | Weighted Average [Member]
Other Intangible Assets [Roll Forward]
Remaining weighted average amortization period (in years)		13 years
Other Amortizing Intangible Assets [Member]
Other Intangible Assets [Line Items]
Other intangible assets, amortizing, gross carrying amount	[1]				19,800
Accumulated amortization	[1]				(10,200)
Other Intangible Assets [Roll Forward]
Other intangible assets, net, amortizing, beginning balance	[1]		10,700	9,600
Additions from new business combinations, amortizing intangible assets	[1]		4,200	2,800
Amortization expense	[1]		(1,900)	(1,600)
Currency translation adjustments, amortizing intangible assets	[1]		(200)	(100)
Other intangible assets, net, amortizing, ending balance	[1]	$ 12,800	12,800	10,700	9,600
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
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	0
Currency translation adjustments, non-amortizing intangible assets			0	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		93,300	59,400	31,300	31,300
Other Intangible Assets [Roll Forward]
Other intangible assets, non-amortizing, beginning balance			59,400	31,300
Additions from new business combinations, non-amortizing intangible assets			38,700	29,600
Currency translation adjustments, non-amortizing intangible assets			(4,800)	(1,500)
Other intangible assets, non-amortizing, ending balance		$ 93,300	$ 93,300	$ 59,400	$ 31,300

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