Share-based compensation (Tables)

3 Months Ended

Mar. 31, 2019

Stock Plans

Schedule of share-based compensation expense

	Three months ended March 31,
	2019		2018
	(in thousands)
Cost of sales	$	470	$	554
Research and development		792		954
Selling, general, and administrative		1,895		2,857
Restructuring		—		172
Total	$	3,157	$	4,537

Summary of stock option activity

		Weighted
	Number of	Average
	Shares	Exercise Price
	(in thousands)
Balance -  December 31, 2018	1,222		34.80
Expired or forfeited	(33)		33.82
Balance -  March 31, 2019	1,189		34.83

Summary of non-vested restricted and performance shares activity

		Weighted
		Average
	Number of	Grant Date
	Shares	Fair Value
	(in thousands)
Balance -  December 31, 2018	2,218		20.74
Granted	974		11.32
Performance award adjustments	(9)		32.67
Vested	(156)		21.71
Forfeited	(89)		21.84
Balance -  March 31, 2019	2,938		17.50