Long-Term Debt - Schedule of Long-term Debt (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 550,000	$ 85,000
Term Loan Credit Facility Unamortized Debt Issuance Costs	(1,032)	0
Long-Term Debt	$ 548,968	$ 85,000
Revolving Credit Facility, due March 9, 2023
Debt Instrument [Line Items]
Interest Rate	3.32%	2.75%
Long-term debt, gross	$ 50,000	$ 85,000
Term Loan Credit Facility, due July 31, 2021
Debt Instrument [Line Items]
Interest Rate	3.17%	0.00%
Long-term debt, gross	$ 500,000	$ 0