Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 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 June 30,				Six Months Ended June 30,
	2021		2020		2021		2020
Cost of revenue	$	0.7	$	0.5	$	1.3	$	1.0
Research and development		28.7		12.5		53.0		23.2
Sales and marketing		4.7		3.9		8.6		7.0
General and administrative		9.1		8.7		17.5		14.9
Total stock-based compensation expense	$	43.2	$	25.6	$	80.4	$	46.1

Schedule of Share Based Compensation Stock Option Activity

The following table shows stock option activity for the six months ended June 30, 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		(2.0	)		2.96
Balance as of June 30, 2021		28.1		$	3.49	$	201.0		5.99

Schedule of Share Based Compensation Restricted Stock Units Award Activity

The following table shows a summary of RSU activity for the six months ended June 30, 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		16.2			10.29
Vested		(8.8	)		4.84
Forfeited		(2.1	)		6.33
Unvested as of June 30, 2021		69.8		$	8.45	$	742.6