Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting Information [Line Items]
Intangible asset amortization expense	$ 3.3	$ 2.7	$ 9.6	$ 6.1
Customer contracts and relationships
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets			8 years 9 months 19 days
Operating contracts and licenses
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets			26 years 6 months
Tradenames
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets			7 years 2 months 13 days
Non-compete agreements
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets			2 years 6 months
Other
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets			2 years 7 months 7 days