Other Long-Term Assets - Other Long-Term Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017	Jun. 30, 2017	Dec. 31, 2016
Other Assets Noncurrent Disclosure [Abstract]
Prepaid technology and maintenance support	$ 1,400	$ 1,900
Deferred deployment costs	900	1,200
Prepaid marketing	400
Restricted cash	0	2,675	$ 3,400	$ 4,210
Other		200
Total	$ 2,747	$ 5,960