Long-Term Debt - Summary of Long-Term Debt (Details) - USD ($)		Jun. 30, 2018	Dec. 31, 2017	Sep. 29, 2017
Debt Instrument [Line Items]
Revolving credit facility		$ 243,500,000	$ 77,000,000
Second Lien Facility		200,000,000	200,000,000	$ 200,000,000
Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums	[1],[2]	10,676,000	11,733,000
Debt Instrument, Unamortized Discount		(3,506,000)	(3,839,000)	(4,000,000)
Unamortized Debt Issuance Expense		(7,170,000)	(7,894,000)	$ (8,200,000)
Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net		432,824,000	265,267,000
Long-term Debt		$ 443,500,000	$ 277,000,000

[1] Discount and issuance costs of the Second Lien Facility are being amortized over the term of the underlying loan using the effective-interest method

[2] Issuance costs of the Credit Facility, which represent costs attributable to the access to credit over its contractual term, have been presented as a component of Other assets (see Note 11) and are being amortized over the term of the Credit Facility using the straight-line method.