Long Term Debt - Additional Information (Detail) $ in Millions	1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2016 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Total leverage ratio		1.0	1.0
Fixed charge coverage ratio		3.9	3.9
Long-term debt including current portion		$ 94.1	$ 94.1	$ 96.6
Unamortized Debt Issuance Expense		(2.8)	(2.8)	(3.4)
Promissory Notes [Member]
Debt Instrument [Line Items]
Long-term debt including current portion		$ 0.7	$ 0.7	0.0
One Hundred Million Term Loan [Member]
Debt Instrument [Line Items]
Weighted-average interest rate for five year Term Loan	2.20%	2.50%	2.50%
Principal amount		$ 100.0	$ 100.0
Maturity date			Aug. 28, 2020
Long-term debt including current portion		$ 96.2	$ 96.2	100.0
Two Hundred Million Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Weighted-average interest rate for five year Term Loan		4.50%	3.50%
Principal amount		$ 200.0	$ 200.0
Availability under the revolving credit facility		173.3	173.3
Outstanding letters of credit		26.7	$ 26.7
Maturity date			Aug. 28, 2020
Long-term debt including current portion		$ 0.0	$ 0.0	$ 0.0