Debt and Financing Arrangements (Interest Expense) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Debt Instrument [Line Items]
Interest expense	$ 1,817	$ 1,692	$ 3,597	$ 3,209
2018 Credit Facility [Member]
Debt Instrument [Line Items]
Interest expense	$ 1,800		$ 3,600
2014 Credit Facility [Member]
Debt Instrument [Line Items]
Interest expense		$ 1,700		$ 3,200