Long-term Debt - Schedule of Actual Ratios and Required Ratios Under Financial Covenants (Details) - Senior Credit Facility	6 Months Ended
	Jun. 30, 2018
Debt Instrument [Line Items]
Interest coverage ratio, as defined under the Senior Credit Facility	11.75
Leverage ratio, as defined under the Senior Credit Facility	2.42
Minimum
Debt Instrument [Line Items]
Required coverage ratio	3.00
Maximum
Debt Instrument [Line Items]
Required leverage ratio	3.75