Interim Consolidated Financial Statements - Additional Information (Detail) - USD ($)		3 Months Ended
	Jan. 02, 2018	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Summary Of Significant Accounting Policy [Line Items]
Expected revenue performance obligation		$ 155,425,000		$ 145,207,000
Prepaid expenses and other current assets		18,641,000		18,942,000
Deferred commissions		14,722,000		13,731,000
Other assets		6,942,000		6,231,000
Retained earnings		121,495,000		123,010,000
Total assets		340,736,000		$ 345,200,000
Total revenues		77,749,000	$ 77,194,000
Net loss		$ (1,733,000)	$ 3,030,000
Basic loss per common share		$ (0.10)	$ 0.17
ASU No. 2018-02 [Member]
Summary Of Significant Accounting Policy [Line Items]
Reclassification adjustment to retained earnings for tax effects	$ 26,000
ASC 606 [Member] | Initial Application Period Cumulative Effect Transition [Member]
Summary Of Significant Accounting Policy [Line Items]
Expected revenue performance obligation		$ 7,800,000
Prepaid expenses and other current assets		(5,500,000)
Deferred commissions		900,000
Other assets		600,000
Retained earnings		3,800,000
ASC 606 [Member] | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Summary Of Significant Accounting Policy [Line Items]
Expected revenue performance obligation		(11,200,000)
Total assets		(9,000,000)
Total revenues		(2,300,000)
Net loss		$ 1,500,000
Basic loss per common share		$ 0.09