Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Deferred revenue	$ 14,717,000	$ 14,717,000		$ 17,949,000
Revenue recognized	1,000,000	$ 7,200,000
New accounting pronouncement revenue recognition timing		The Company recognized revenue of $1.0 and $7.2 million during the three and nine months ended September 30, 2019, respectively, from the deferred revenue balance at December 31, 2018. The Company recognizes deferred revenue by first allocating from the beginning deferred revenue balance to the extent that the beginning deferred revenue balance exceeds the revenue to be recognized. Billings during the period are added to the deferred revenue balance to be recognized in future periods. To the extent that the beginning deferred revenue balance is less than revenue to be recognized during the period, billings during the period are allocated to revenue.
Capitalized contract costs	0	$ 0		$ 0
Lease liability	6,412,000	6,412,000
Operating lease, right-of-use asset	$ 5,634,000	$ 5,634,000
Accounting Standards Update 2016-02 [Member]
Significant Accounting Policies [Line Items]
Lease liability			$ 7,500,000
Operating lease, right-of-use asset			$ 6,700,000
Maximum [Member]
Significant Accounting Policies [Line Items]
Expenses incremental costs expiration period		1 year
Period of Transfer of promised goods or services to customer		1 year