Segment Information - Sales and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 133,143	$ 114,092	$ 376,381	$ 414,274
Gross Profit	58,962	46,331	164,034	171,958
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	115,229	94,018	323,924	359,007
Gross Profit	52,434	37,574	145,432	151,654
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	17,914	20,074	52,457	55,267
Gross Profit	$ 6,528	$ 8,757	$ 18,602	$ 20,304