Fair Value Measurement (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Impairment loss as a result of goodwill	$ 0	$ 0	$ 0
Credit facility, net of original discount on borrowings and deferred financing costs | Carrying Amount
Fair Value Measurement
Long-term borrowings	371,200,000	151,000,000
Credit facility, net of original discount on borrowings and deferred financing costs | Fair Value
Fair Value Measurement
Long-term borrowings	371,200,000	151,000,000
Other obligations | Carrying Amount
Fair Value Measurement
Long-term borrowings	15,400,000	2,800,000
Other obligations | Fair Value
Fair Value Measurement
Long-term borrowings	$ 15,400,000	$ 2,800,000