Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

The following table summarizes the Company’s stock option activity and related information for the year ended December 31, 2021:

	Number of Options	Weighted Average Exercise Price		Weighted-Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (millions)
Balance outstanding as of December 31, 2020	4,429,489	$	58.82
Granted	1,012,211	$	177.84
Exercised	(673,095)	$	41.54
Forfeited and expired	(236,353)	$	108.53
Balance outstanding as of December 31, 2021	4,532,252	$	85.38	6.9	$	311.7
Options exercisable at December 31, 2021	2,685,192	$	50.44	5.7	$	261.2

Schedule of Assumptions Used in Fair Value Estimates

The assumptions used for the specified reporting periods and the resulting estimates of weighted-average estimated fair value per share of options granted during those periods are as follows:

	Year Ended December 31,
	2021	2020	2019
Risk-free interest rate	0.8%	1.1%	2.2%
Dividend yield	—%	—%	—%
Volatility factor	76.9%	81.5%	82.1%
Expected term (in years)	5.1	5.6	5.6
Weighted average estimated fair value per share	$110.43	$77.92	$52.03

Schedule of Restricted Stock Units Activity and Performance Stock Units Activity

A summary of the Company’s RSU activity for the year ended December 31, 2021 is as follows:

	Number of RSUs	Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value (millions)
Balance outstanding as of December 31, 2020	450,260	$	114.58
Granted	484,409	$	182.35
Releases	(148,551)	$	117.35
Canceled/forfeited	(65,551)	$	147.70
Balance outstanding as of December 31, 2021	720,567	$	156.55	$	105.7

A summary of the Company’s PSU activity for the year ended December 31, 2021 is as follows:

	Number of PSUs	Weighted Average Grant Date Fair Value		Aggregate Intrinsic Value (millions)
Balance outstanding as of December 31, 2020	15,000	$	101.00
Granted	323,337	$	158.96
Releases	(3,428)	$	212.93
Canceled/forfeited	(53,298)	$	146.48
Balance outstanding as of December 31, 2021	281,611	$	157.58	$	41.3

Schedule of Share-based Compensation Expense

Total share-based compensation expense by consolidated statement of operations and comprehensive loss classification is presented below (in thousands):

	Year ended December 31,
	2021		2020		2019
Research and development expense	$	68,496	$	48,044	$	31,024
General and administrative expense	45,006		37,803		24,513
	$	113,502	$	85,847	$	55,537