Debt - Certain Covenants (Details) - Second Amended and Restated Credit Agreement	9 Months Ended
	Sep. 30, 2018
Revolving Credit Facility
Debt Instrument [Line Items]
Percentage of utilized line of credit	25.00%
Lines of credit
Debt Instrument [Line Items]
Maximum debt to consolidated EBITDA ratio	4.75
Lines of credit | Revolving Credit Facility | June 30, 2018 and thereafter
Debt Instrument [Line Items]
Required minimum Debt to Consolidated EBITDA ratio	3.5