Supplemental Financial Statement Information - Additional Information (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized contract acquisition costs					$ 8,100,000
Amortization of deferred contract acquisition costs		$ 4,400,000
Impairment loss of capitalized contract acquisition costs		0
Capitalized contract cost increase (decrease)		4,900,000
Deferred cost of revenue		400,000	$ 3,500,000
Reclassification adjustments included in net income, net of tax	[1]	$ (19,000)	$ 140,000	$ 0
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred sales commissions amortization period		3 years
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred sales commissions amortization period		4 years

[1] Tax effect was less than $0.1 million for each of the periods presented above.