Debt - Additional Information (Detail) - USD ($)		3 Months Ended
	Jul. 14, 2017	Mar. 31, 2018	Dec. 31, 2017	Jul. 13, 2017	Mar. 31, 2017
Line of Credit Facility [Line Items]
Revolving credit borrowing		$ 142,600,000	$ 99,200,000		$ 76,300,000
Letters of credit outstanding		3,600,000
Capital lease and other obligations		4,100,000	$ 3,800,000		$ 3,200,000
Minimum [Member]
Line of Credit Facility [Line Items]
Fall of excess committed borrowing availability		17,500,000
Maximum [Member]
Line of Credit Facility [Line Items]
Fall of excess committed borrowing availability		31,300,000
Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, expiration date	Jul. 14, 2022
Amortization period on real estate component of borrowing base	12 years 6 months
Revolving credit borrowing		$ 142,600,000
Weighted average interest rate		3.40%
Excess committed borrowing availability		$ 43,900,000
Unused commitment fees		0.25%
Fixed charge coverage ratio of credit facility		100.00%
Revolving Credit Facility [Member] | Asset Backed Securities [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 250,000,000			$ 160,000,000
Line of credit facility, conditional maximum borrowing capacity	300,000,000
Uncommitted conditional increased borrowing capacity during period	$ 50,000,000