Goodwill and Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Goodwill [Line Items]
Goodwill, relates to acquisition	$ 3,500,000		$ 3,500,000
Impairment losses	0
Amortization expense	400,000	$ 1,100,000
Network Solutions [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition	3,100,000
Services & Support [Member]
Goodwill [Line Items]
Goodwill, relates to acquisition	$ 400,000