Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2021

Equity [Abstract]

Schedule of Shares of Common Stock Reserved for Future Issuance

The following shares of the Company's common stock were reserved for future issuance at December 31, 2021 (in thousands):

Shares reserved for issuance upon conversion of Convertible Senior Notes	2,554
Shares underlying outstanding warrants	215
Shares underlying outstanding stock options	4,814
Shares underlying unvested restricted stock units	612
Shares authorized for issuance pursuant to awards granted under the ESPP	1,216
Shares authorized for future equity award grants	1,382
	10,793

Schedule of Stockholders' Equity Common Stock Warrants

Warrants outstanding to purchase shares of the Company's common stock as of December 31, 2021 were as follows:

Issue Date	Exercise Price Per Share	Warrants Outstanding	Expiration Date of Warrants Outstanding
October 2017	$3.50	1,000	October 2022
March 2017	$23.50	193,788	March 2027
August 2011 - August 2012	$73.73	19,722	May 2022 - August 2022
		214,510

Schedule of Stock Option Activities for 2006 Plan and 2013 Plan

The following table summarizes stock option activities for the 2006 Plan and 2013 Plan:

	Total Options	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2019	7,174,927	$	38.40	8.45	$	181,408
Granted	1,130,040	$	83.55
Exercised	(2,339,467)	$	24.69		$	161,688
Canceled/forfeited/expired	(161,995)	$	27.00		$	4,516
Outstanding at December 31, 2020	5,803,505	$	52.08	7.90	$	268,649
Granted	355,008	$	86.68
Exercised	(1,128,791)	$	37.05		$	86,149
Canceled/forfeited/expired	(215,372)	$	76.29		$	6,963
Outstanding at December 31, 2021	4,814,350	$	57.08	7.07	$	452,081
Vested and expected to vest at December 31, 2021	4,769,317	$	56.95	7.06	$	448,460
Exercisable at December 31, 2021	3,013,030	$	49.28	6.50	$	307,235

Schedule of Restricted Stock Units

A summary of RSU activity for the years ended December 31, 2021 and 2020 is as follows:

	Total RSUs	Weighted-Average Grant Date Fair Value		Aggregate Intrinsic Value (in thousands)
Unvested awards outstanding at December 31, 2019	—	$	—	$	—
Granted	134,694	$	82.82
Vested	(1,892)	$	95.68
Unvested awards outstanding at December 31, 2020	132,802	$	82.82	$	12,706
Granted	564,034	$	96.37
Vested	(53,957)	$	82.74
Canceled/forfeited	(30,705)	$	87.21
Unvested awards outstanding at December 31, 2021	612,174	$	95.11	$	92,144

Schedule of Compensation Cost Included in Consolidated Statement of Operations

The following table summarizes the allocation of stock-based compensation expense included in the consolidated statements of operations for all stock-based compensation arrangements (in thousands):

	Year Ended December 31,
	2021		2020		2019
Cost of sales	$	6,434	$	8,210	$	6,415
Selling, general & administrative	43,567		41,563		42,857
Research and development	10,751		8,658		8,799
Total stock-based compensation expense	$	60,752	$	58,431	$	58,071

Schedule of Assumptions Used in Black-Scholes Option-Pricing Model

The assumptions used in the Black-Scholes option-pricing model are as follows:

	Stock Options
	Year Ended December 31,
	2021			2020			2019
Weighted average grant date fair value (per share)	$	56.89		$	54.20		$	39.06
Risk-free interest rate	1.0		%	0.6		%	2.1		%
Expected dividend yield	0.0		%	0.0		%	0.0		%
Expected volatility	75.1		%	74.6		%	71.8		%
Expected term (in years)	6.1			6.1			6.0

	ESPP
	Year Ended December 31,
	2021			2020			2019
Weighted average grant date fair value (per share)	$	38.19		$	36.83		$	30.32
Risk-free interest rate	0.2		%	0.2		%	1.9		%
Expected dividend yield	0.0		%	0.0		%	0.0		%
Expected volatility	44.2		%	60.3		%	69.9		%
Expected term (in years)	1.3			1.3			1.3