Allowance for Doubtful Accounts Receivable and Sales Returns (Additional Information) (Detail)	12 Months Ended
	Dec. 31, 2020 USD ($) Customer	Dec. 31, 2019 USD ($) Customer
Accounts Receivable
Concentration Risk [Line Items]
Number of major customers	2	2
Percentage by major customer	10.00%	1000.00%
Accounts Receivable | Company A
Concentration Risk [Line Items]
Percentage by major customer	19.00%	26.00%
Accounts Receivable | Company B
Concentration Risk [Line Items]
Percentage by major customer	10.00%	11.00%
Revenue by Segment
Concentration Risk [Line Items]
Percentage by major customer	25.00%	13.00%
Revenues | $	$ 17,300,000	$ 8,800,000
Mobile Services | Revenue by Segment
Concentration Risk [Line Items]
Number of major customers	2	1