Long-Term Debt - Schedule of Long-Term Debt (Detail) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017	Jan. 01, 2018
Debt Instrument [Line Items]
Total debt, excluding deferred financing costs	$ 705,877	$ 709,470
Deferred financing costs, net of accumulated amortization	(4,735)	(5,709)
Total debt	701,142	703,761
Current portion of long-term debt and line of credit	7,185	7,185	$ 7,185
Long-term debt, net of current maturities	693,957	696,576	$ 696,576
Revolving Credit Facility
Debt Instrument [Line Items]
Total debt, excluding deferred financing costs	$ 0	$ 0
Total rate - base plus spread	6.75%	6.25%
Term Loan B
Debt Instrument [Line Items]
Total debt, excluding deferred financing costs	$ 705,877	$ 709,470
Total rate - base plus spread	4.89%	4.59%