Interim Consolidated Financial Statements - Summary of Effect of Adopting ASC 606 In Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Accounts receivable, net	$ 62,154	$ 70,023
Deferred commissions	14,722	13,731
Prepaid expenses and other current assets	18,641	18,942
Total current assets	231,848	236,819
Other assets	6,942	6,231
Total assets	340,736	345,200
Deferred revenue	155,425	145,207
Total current liabilities	191,038	195,053
Total liabilities	199,441	204,011
Retained earnings	121,495	123,010
Total stockholders’ equity	141,295	141,189
Total liabilities and stockholders’ equity	340,736	$ 345,200
ASC 606 [Member] | Amounts as if Previous Guidance in Effect [Member]
Accounts receivable, net	67,826
Deferred commissions	13,791
Prepaid expenses and other current assets	23,427
Total current assets	241,375
Other assets	6,380
Total assets	349,702
Deferred revenue	166,669
Total current liabilities	202,282
Total liabilities	210,685
Retained earnings	119,217
Total stockholders’ equity	139,017
Total liabilities and stockholders’ equity	$ 349,702