Stock Plans (Tables)

12 Months Ended

Dec. 31, 2018

Stock Plans

Schedule of share-based compensation expense

	For the year ended December 31,
	2018		2017		2016
	(in thousands)
Cost of sales	$	1,885	$	2,505	$	1,956
Research and development		3,611		2,957		3,324
Selling, general, and administrative		9,417		12,851		10,433
Restructuring		1,161		1,880		—
Acquisition costs		—		4,203		—
Total	$	16,074	$	24,396	$	15,713

Summary of unrecognized share-based compensation costs

	Unrecognized		Weighted
	Share-Based		Average Period
	Compensation		Expected to be
	Costs		Recognized
	(in thousands)		(in years)
Stock option awards	$	—	—
Restricted stock units		2,466	2.4
Restricted stock awards		19,663	2.6
Performance share units		7,356	2.4
Total unrecognized share-based compensation cost	$	29,485	2.5

Schedule of options, vested and expected to vest

				Weighted
	Number	Weighted		Average	Aggregate
	of	Average		Remaining	Intrinsic
	Shares	Exercise Price		Contractual Life	Value
	(in thousands)			(in years)	(in thousands)
Vested	1,222	$	34.80	3.0	—
Expected to vest	—		—	—	—
Total	1,222		34.80	3.0	—

Summary of stock option activity

		Weighted
	Number of	Average
	Shares	Exercise Price
	(in thousands)
Balance -  December 31, 2015	2,064	$	32.91
Granted	—		—
Exercised	(194)		12.18
Expired or forfeited	(294)		34.44
Balance -  December 31, 2016	1,576		35.18
Granted	—		—
Exercised	(18)		30.03
Expired or forfeited	(164)		37.47
Balance -  December 31, 2017	1,394		34.97
Granted	—		—
Exercised	—		—
Expired or forfeited	(172)		36.21
Balance -  December 31, 2018	1,222		34.80

Summary of information about stock option information

	Options Outstanding						Options Exercisable
				Weighted						Weighted
		Aggregate		Average	Weighted			Aggregate		Average	Weighted
		Intrinsic		Remaining	Average			Intrinsic		Remaining	Average
Range of Exercise Prices	Shares	Value		Contractual Life	Exercise Price		Shares	Value		Contractual Life	Exercise Price
	(in thousands)	(in thousands)		(in years)			(in thousands)	(in thousands)		(in years)
$20.00 - $30.00	25	$	—	3.6	$	28.13	25	$	—	3.6	$	28.13
$30.01 - $40.00	1,058		—	3.1		32.81	1,058		—	3.1		32.81
$40.01 - $50.00	12		—	1.7		45.57	12		—	1.7		45.57
$50.01 - $60.00	127		—	2.4		51.70	127		—	2.4		51.70
	1,222	$	—	3.0		34.80	1,222	$	—	3.0		34.80

Summary of information on options exercised

	Year ended December 31,
	2018		2017		2016
	(in thousands)
Cash received from options exercised	$	—	$	431	$	494
Intrinsic value of options exercised	$	—	$	51	$	1,165

Summary of non-vested restricted and performance shares activity

		Weighted
		Average
	Number of	Grant Date
	Shares	Fair Value
	(in thousands)
Balance -  December 31, 2015	1,398	$	31.97
Granted	1,166		17.59
Vested	(349)		32.73
Forfeited	(266)		27.31
Balance -  December 31, 2016	1,949		23.85
Granted	674		29.22
Performance award adjustments	(25)		20.95
Assumed from Ultratech	338		31.75
Vested	(831)		27.67
Forfeited	(225)		26.29
Balance -  December 31, 2017	1,880		25.41
Granted	1,257		17.37
Performance award adjustments	(5)		32.67
Vested	(523)		26.39
Forfeited	(391)		24.66
Balance -  December 31, 2018	2,218		20.74

Summary of valuation assumptions for performance awards

	Year ended December 31,
	2018
Weighted average fair value	$	15.58
Dividend yield		0	%
Expected volatility factor(1)		49	%
Risk-free interest rate(2)		2.88	%
Expected life (in years)(3)		3.0

(1) Expected volatility is measured using historical daily price changes of the Company’s stock over the respective expected term.

(2) The risk-free rate for periods within the contractual term is based on the U.S. Treasury yield curve in effect at the time of grant.

(3) The expected life is the number of years the Company estimates that the awards will be outstanding prior to exercise.

Summary of valuation assumptions for employee stock purchase plan

		Year ended December 31,
	2018			2017			2016
Weighted average fair value	$	4.94		$	7.09		$	4.45
Dividend yield		0	%		0	%		0	%
Expected volatility factor(1)		62	%		36	%		43	%
Risk-free interest rate(2)		1.81	%		0.99	%		0.35	%
Expected life (in years)(3)		0.5			0.5			0.5

(1) Expected volatility is measured using historical daily price changes of the Company’s stock over the respective expected term.

(2) The risk-free rate for periods within the contractual term is based on the U.S. Treasury yield curve in effect at the time of grant.

(3) The expected life is the number of years the Company estimates that the purchase rights will be outstanding prior to exercise.