Accounts Receivable, Net and Revenue Concentrations (Tables)

6 Months Ended

Jun. 30, 2019

Changes in the allowance for doubtful accounts were as follows:



(In thousands)	Six Months Ended June 30,
(In thousands)	2019			2018
Balance at beginning of period	$	1,121		$	1,064
Additions to costs and expenses	5			2
(Write-offs)/Foreign exchange effects	(4		)	(58		)
Balance at end of period	$	1,122		$	1,008

Accounts receivable, net were as follows:



(In thousands)	June 30, 2019			December 31, 2018
Trade receivables, gross	$	150,779		$	133,774
Allowance for doubtful accounts	(1,122		)	(1,121		)
Allowance for sales returns	(582		)	(731		)
Net trade receivables	149,075			131,922
Other	5,558			12,767
Accounts receivable, net	$	154,633		$	144,689

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

⁽¹⁾ Net sales to this customer did not total more than 10% of our total net sales in the prior period.

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

⁽¹⁾ Trade receivables associated with this customer did not total more than 10% of our accounts receivable, net at December 31, 2018.

The pattern of revenue recognition was as follows:



	Three Months Ended June 30,				Six Months Ended June 30,
(In thousands)	2019		2018		2019		2018
Goods and services transferred at a point in time	$	99,632	$	83,661	$	201,776	$	177,600
Goods and services transferred over time	94,264		78,862		176,283		149,621
Net sales	$	193,896	$	162,523	$	378,059	$	327,221