Revenue Recognition - Schedule of Significant Changes in Contract Assets and Deferred Revenue (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Changes in the Contract Assets
Transferred to receivables from contract assets recognized at December 31, 2018		$ 302
Revenue recognized that was included in contract assets at December 31, 2018	$ 204	1,189
Changes in the Contract Liabilities
Revenue recognized that was included in deferred revenue at December 31, 2018		$ 984