Allowance for Doubtful Accounts Receivable and Sales Returns (Additional Information) (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Concentration Risk [Line Items]
Revenue	[1]	$ 33,112	$ 29,734	$ 63,687	$ 57,964
Accounts Receivable
Concentration Risk [Line Items]
Percentage by major customer				60.00%		64.00%
Revenue by Segment | Mobile Services
Concentration Risk [Line Items]
Percentage by major customer		35.00%	33.00%	35.00%	31.00%
Revenue		$ 11,500	$ 9,700	$ 22,400	$ 18,100

[1] Quarters ended June 30, Components of Revenue2017 2016License Fees9,084 6,678Service Revenue24,028 23,056Net Revenue33,112 29,734 Six Months Ended June 30, Components of Revenue2017 2016License Fees$15,677 $12,455Service Revenue48,010 45,509Net Revenue$63,687 $57,964