Goodwill and Other Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Intangible asset amortization expense	$ 2.7	$ 3.1
Customer contracts and relationships
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets	8 years 3 months 18 days
Operating contracts and licenses
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets	26 years 1 month 6 days
Tradenames
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets	6 years 9 months 18 days
Non-compete agreements
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets	2 years
Other
Segment Reporting Information [Line Items]
Weighted-average amortization period of intangible assets	8 years 3 months 18 days