Significant Concentrations - Additional Information (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Concentration Risk [Line Items]
Expiration date one of OEM Distribution agreements for embedded operating systems	Jun. 30, 2018
Expiration date of OEM Distribution agreements for mobile operating systems, non-EMEA	Jun. 30, 2018
Rebate credits outstanding	$ 411,000
Cost of revenue [Member]
Concentration Risk [Line Items]
Allocation of rebate values, percentage	30.00%
Reduction in marketing expense [Member]
Concentration Risk [Line Items]
Allocation of rebate values, percentage	70.00%