Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost		$ 1,733	$ 1,751	$ 1,716
Return on assets (expected)		(895)	(795)	(839)
Amortization of net actuarial loss (gain)	[1]	552	544	834
Net periodic pension cost		1,390	1,500	1,711
Non-U.S. Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost		664	703	738
Interest cost		486	614	661
Return on assets (expected)		(323)	(275)	(176)
Amortization of net actuarial loss (gain)	[1]	(78)	(70)	529
Settlement charge			(178)
Adjustments			(1,849)
Foreign currency			(31)
Net periodic pension cost		$ 749	$ (1,086)	$ 1,752

[1] ARRIS uses the allowable 10% corridor approach to determine the amount of gains/losses subject to amortization in pension cost. Gains/losses are amortized on a straight-line basis over the average future service of members expected to receive benefits