Accounts Receivable, Net and Revenue Concentrations (Tables)

3 Months Ended

Mar. 31, 2018

Receivables [Abstract]

Accounts Receivable, Net and Allowance for Doubtful Accounts

Changes in the allowance for doubtful accounts were as follows:

(In thousands)	Three Months Ended March 31,
	2018		2017
Balance at beginning of period	$	1,064	$	904
Additions to costs and expenses	4		23
(Write-offs)/Foreign exchange effects	9		18
Balance at end of period	$	1,077	$	945

Accounts receivable, net were as follows:

(In thousands)	March 31, 2018			December 31, 2017
Trade receivables, gross	$	154,181		$	142,299
Allowance for doubtful accounts	(1,077		)	(1,064		)
Allowance for sales returns	(539		)	(562		)
Net trade receivables	152,565			140,673
Other	7,490			10,905
Accounts receivable, net	$	160,055		$	151,578

Net Sales to Significant Customers

Net sales to the following customers totaled more than 10% of our net sales:

	Three Months Ended March 31,
	2018				2017
	$ (thousands)		% of Net Sales		$ (thousands)		% of Net Sales
Comcast Corporation	$	37,975	23.1	%	$	42,247	26.2	%
AT&T (1)	$	—	—	%	$	19,200	11.9	%

⁽¹⁾   Sales associated with this customer did not total more than 10% of our net sales as of March 31, 2018.

Trade Receivables Associated with Significant Customers

Trade receivables associated with these significant customers that totaled more than 10% of our accounts receivable, net were as follows:

	March 31, 2018				December 31, 2017
	$ (thousands)		% of Accounts Receivable, Net		$ (thousands)		% of Accounts Receivable, Net
Comcast Corporation	$	27,372	17.1	%	$	25,142	16.6	%