Long-Term Debt - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total indebtedness	$ 41,400	$ 69,055
Secured Revolving Credit Facility
Debt Instrument [Line Items]
Average line of credit facility outstanding	$ 59,897	$ 94,765
Weighted average interest rate	2.30%	2.10%	2.50%
Maximum
Debt Instrument [Line Items]
Capacity to increase borrowings under credit agreement	$ 104,853