Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2021

Equity [Abstract]

Stock-Based Compensation Expense Related to Grants of Employee Stock Options, Restricted Stock Units (RSUs) and Performance and Market Based Awards

We recorded stock-based compensation expense related to grants of employee stock options, restricted stock units (“RSUs”) and performance and market-based awards in our consolidated statements of operations as follows (in millions):

	Three Months Ended March 31,
	2021		2020
Cost of revenue	$	0.6	$	0.4
Research and development		24.3		10.7
Sales and marketing		3.9		3.1
General and administrative		8.4		6.3
Total stock-based compensation expense	$	37.2	$	20.5

Schedule of Share Based Compensation Stock Option Activity

The following table shows stock option activity for the three months ended March 31, 2021 (in millions, except weighted-average exercise price and weighted-average contractual term):

	Outstanding Options
						Aggregate		Weighted-
				Weighted-Average		Intrinsic Value of		Average
				Exercise Price		Stock Options		Contractual Term
	Stock Options			(per option)		Outstanding		(in years)
Balance as of December 31, 2020		30.1		$	3.46	$	193.1		6.43
Granted		—			—
Forfeited, expired and cancelled		—			—
Exercised		(1.9	)		2.96
Balance as of March 31, 2021		28.2		$	3.49	$	189.8		6.22

Schedule of Share Based Compensation Restricted Stock Units Award Activity

The following table shows a summary of RSU activity for the three months ended March 31, 2021, which includes performance and market-based awards (in millions, except weighted-average grant date fair value):

	Outstanding RSUs
				Weighted-Average		Aggregate
				Grant Date Fair Value		Intrinsic Value of
	Shares			(per share)		Unvested RSUs
Unvested as of December 31, 2020		64.5		$	7.43	$	636.0
Granted		14.9			10.28
Vested		(5.3	)		4.84
Forfeited		(1.1	)		5.68
Unvested as of March 31, 2021		73.0		$	8.22	$	744.8

Common Stock Reserved For Future Issuance

As of March 31, 2021, we had reserved shares of common stock for future issuance as follows, which reflects additional shares reserved under our 2011 Equity Incentive Plan and 2011 Employee Stock Purchase Plan (in millions):

	March 31, 2021
Stock options outstanding		28.2
RSUs outstanding		73.0
2011 Equity Incentive Plan		176.7
2011 Employee Stock Purchase Plan		160.4
Total		438.3