Debt - Schedule of Long-Term Debt Components (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Current maturities of long-term debt	$ 6,072	$ 6,079
Total long-term debt	524,100	498,300
Transaction Costs	(5,500)	(6,300)
Total Debt	524,700	498,100
Term Loan [Member]
Debt Instrument [Line Items]
Total long-term debt	63,900	67,000
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Total long-term debt	211,600	181,300
First In Last Out Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Total long-term debt	98,600	100,000
2017 Credit Agreement [Member]
Debt Instrument [Line Items]
Current maturities of long-term debt	6,100	6,100
2013 Note Purchase Agreement [Member]
Debt Instrument [Line Items]
Total long-term debt	$ 150,000	$ 150,000