Interim Consolidated Financial Statements - Summary of Effect of Adopting ASC 606 In Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts receivable, net	$ 49,486	$ 70,023
Deferred commissions	12,514	13,731
Prepaid expenses and other current assets	12,789	18,942
Total current assets	217,876	236,819
Other assets	7,756	6,231
Total assets	326,142	345,200
Deferred revenue	143,023	145,207
Total current liabilities	177,937	195,053
Total liabilities	186,031	204,011
Retained earnings	125,698	123,010
Total stockholders’ equity	140,111	141,189
Total liabilities and stockholders’ equity	326,142	$ 345,200
ASC 606 [Member] | Amounts as if Previous Guidance in Effect [Member]
Accounts receivable, net	53,040
Deferred commissions	11,734
Prepaid expenses and other current assets	17,573
Total current assets	225,434
Other assets	7,194
Total assets	333,138
Deferred revenue	152,033
Total current liabilities	186,947
Total liabilities	195,041
Retained earnings	123,684
Total stockholders’ equity	138,097
Total liabilities and stockholders’ equity	$ 333,138