Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2023

Stockholders' Equity [Abstract]

Stock Option Activity

The following table summarizes the stock option activity under our stock plans for the year ended December 31, 2023 (in thousands, except per share and contractual life data):

	Number of Shares			Weighted Average Exercise Price Per Share		Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding at December 31, 2022		14,970		$	50.57
Granted		2,407		$	38.80
Exercised		(1,444	)	$	45.06
Cancelled/forfeited/expired		(1,842	)	$	55.90
Outstanding at December 31, 2023		14,091		$	48.43		4.74	$	78,542
Exercisable at December 31, 2023		9,703		$	52.24		3.20	$	28,349

Restricted Stock Unit Activity

The following table summarizes the RSU activity for the year ended December 31, 2023 (in thousands, except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Non-vested at December 31, 2022		2,766		$	48.30
Granted		1,707		$	40.51
Vested		(1,055	)	$	51.64
Cancelled/forfeited		(179	)	$	42.90
Non-vested at December 31, 2023		3,239		$	43.40

Performance Restricted Stock Unit Activity

The following table summarizes the PRSU activity for the year ended December 31, 2023 (in thousands, except per share data):

	Number of Shares			Weighted Average Grant Date Fair Value Per Share
Non-vested at December 31, 2022		143		$	52.59
Granted		158		$	57.43
Vested		(75	)	$	52.43
Non-vested at December 31, 2023		226		$	56.04

Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the years ended December 31, 2023, 2022 and 2021 (in thousands):

	Year Ended December 31,
	2023		2022		2021
Cost of sales	$	499	$	533	$	456
Research, development and patent		77,826		73,704		87,522
Selling, general and administrative		27,484		26,027		32,700
Total	$	105,809	$	100,264	$	120,678

Weighted-Average Assumptions for Stock Options

Employee Stock Options:

	Year Ended December 31,
	2023			2022			2021
Risk-free interest rate		3.8	%		2.1	%		0.6	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		46.8	%		54.5	%		54.0	%
Expected life	6.3 years			6.3 years			4.9 years

Board of Director Stock Options:

	Year Ended December 31,
	2023			2022			2021
Risk-free interest rate		3.8	%		2.9	%		1.2	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		52.7	%		56.2	%		55.9	%
Expected life	7.7 years			7.4 years			7.3 years

Weighted-Average Assumptions for ESPP

ESPP:

	Year Ended December 31,
	2023			2022			2021
Risk-free interest rate		5.3	%		1.2	%		0.1	%
Dividend yield		0.0	%		0.0	%		0.0	%
Volatility		36.0	%		50.1	%		42.4	%
Expected life	6 months			6 months			6 months