Allowance for Doubtful Accounts Receivable and Sales Returns (Additional Information) (Detail) $ in Thousands	3 Months Ended							12 Months Ended
	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) Customer	Dec. 31, 2018 USD ($) Customer
Concentration Risk [Line Items]
Net revenue	$ 44,993	$ 44,248	$ 39,472	$ 16,557	$ 17,579	$ 15,724	$ 19,650
Accounts Receivable
Concentration Risk [Line Items]
Percentage by major customer								10.00%	1000.00%
Accounts Receivable | Company A
Concentration Risk [Line Items]
Percentage by major customer								31.00%	2300.00%
Accounts Receivable | Company B
Concentration Risk [Line Items]
Percentage by major customer								11.00%	1100.00%
Accounts Receivable | Company C
Concentration Risk [Line Items]
Percentage by major customer								10.00%	1000.00%
Mobile Services | Revenue by Segment
Concentration Risk [Line Items]
Number of major customers | Customer								1	1
Percentage by major customer								14.00%	11.00%
Net revenue								$ 23,800	$ 7,700