Business Acquisitions (Details) - USD ($) $ in Millions	1 Months Ended		12 Months Ended
	Nov. 30, 2016	Feb. 28, 2014	Dec. 31, 2016	Dec. 31, 2014	Dec. 31, 2015
Business Acquisitions
Cash paid for acquisition, net of cash acquired			$ 140.0	$ 35.7
Goodwill			578.1	$ 484.5	$ 484.1
Radiant
Business Acquisitions
Cash paid for acquisition, net of cash acquired	$ 135.1
Goodwill	90.0
Acquired intangible assets	62.1
Net liabilities excluding cash acquired	$ 17.0
Time period in which the valuation of acquisition will be completed	1 year
Pro-forma operating revenue			$ 825.3
Spatial Energy
Business Acquisitions
Cash paid for acquisition, net of cash acquired		$ 35.7
Goodwill		25.7
Goodwill associated with acquisition that is deductible for income tax purposes		19.0
Acquired intangible assets		13.9
Liabilities accrued in consideration for business acquisition		$ 3.9