Joint Venture and Related Party Transactions - Summarized Financial Data (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Current assets	$ 49,644				$ 76,313				$ 49,644	$ 76,313
Current liabilities	4,318				5,038				4,318	5,038
Noncurrent liabilities	854				985				854	985
Gross profit	3,126	$ 2,979	$ 3,233	$ 3,428	2,801	$ 6,605	$ 3,467	$ 3,782	12,766	16,655
Operating expenses									46,290	43,220
TVaura Mobile LLC [Member]
Related Party Transaction [Line Items]
Current assets	31				35				31	35
Noncurrent assets	0				0				0	0
Current liabilities	12				12				12	12
Noncurrent liabilities	$ 0				$ 0				0	0
Revenue									0	0
Gross profit									0	0
Operating expenses									5	5
Net loss from continuing operations									(5)	(5)
The Company's pro-rata share—net loss									0	0
The Company's loss on investment									$ 0	$ 0