Long-Term Debt - Additional Information (Detail) - USD ($)	6 Months Ended	9 Months Ended
	Jun. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Sep. 29, 2017
Debt Disclosure [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 237,500,000
Debt Issuance Costs, Line of Credit Arrangements, Gross	$ 700,000
Interest Coverage Ratio, Maximum	3.00
Current Ratio	1.00
Second Lien Facility	$ 200,000,000		$ 200,000,000	$ 200,000,000
Proceeds from Debt, Net of Issuance Costs		$ 187,800,000
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, Discounted Percentage	98.00%
Year 2 [Member]
Debt Disclosure [Line Items]
Prepayment Premium	102.00%
Prepayment Premium, Change in Control	102.00%
Year 3 [Member]
Debt Disclosure [Line Items]
Prepayment Premium	101.00%
Prepayment Premium, Change in Control	101.00%
Revolving Credit Facility
Debt Disclosure [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 340,000,000
Interest Rate at Period End	5.58%
Revolving Credit Facility | Future Period Three [Member]
Debt Disclosure [Line Items]
Debt To E B I T D Ratio Maximum	3.50
Letter of Credit
Debt Disclosure [Line Items]
Line of Credit Facility, Unused Capacity, Commitment Fee Percentage	0.50%
Line of Credit [Member]
Debt Disclosure [Line Items]
Letters of Credit Outstanding, Amount	$ 800,000		$ 800,000
Line of Credit [Member] | Letter of Credit
Debt Disclosure [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 5,000,000.0
Second Lien Facility [Member]
Debt Disclosure [Line Items]
Interest rate option one, applicable margin rate over Adjusted LIBOR	7.00%
Interest rate option two, applicable margin rate	6.00%
Second Lien Facility, Initial Interest Rate	9.10%	8.34%
Second Lien Facility, Effective Interest Rate	9.89%
Minimum [Member] | Revolving Credit Facility
Debt Disclosure [Line Items]
Interest rate option one, applicable margin rate over Adjusted LIBOR	2.00%
Interest rate option two, applicable margin rate	3.00%
Maximum [Member] | Revolving Credit Facility
Debt Disclosure [Line Items]
Interest rate option one, applicable margin rate over Adjusted LIBOR	3.00%
Interest rate option two, applicable margin rate	4.00%
Interest Payable One [Member] | Revolving Credit Facility
Debt Disclosure [Line Items]
Debt Instrument, Interest Payable Period	1 month
Interest Payable Two [Member] | Revolving Credit Facility
Debt Disclosure [Line Items]
Debt Instrument, Interest Payable Period	3 months
Interest Payable Three [Member] | Revolving Credit Facility
Debt Disclosure [Line Items]
Debt Instrument, Interest Payable Period	6 months