Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Jun. 30, 2019
Common Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Common stock, authorized (in shares)	200,000,000		200,000,000		200,000,000
Common stock, issued (in shares)	72,017,145		72,017,145		70,264,265
Common stock, outstanding (in shares)	69,307,315		69,307,315		67,554,435
Common stock, par value (in dollars per share)	$ 0.001		$ 0.001		$ 0.001	$ 0.001
Preferred Stock, Number of Shares, Par Value and Other Disclosures [Abstract]
Preferred stock, authorized (in shares)	5,000,000		5,000,000		5,000,000
Preferred stock, issued (in shares)	0		0		0
Preferred stock, shares outstanding (in shares)	0		0		0
Preferred stock, par value (in dollars per share)	$ 0.001		$ 0.001		$ 0.001
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock, authorized (in shares)	200,000,000		200,000,000		200,000,000
Common stock, issued (in shares)	72,017,145		72,017,145		70,264,265
Common stock, outstanding (in shares)	69,307,315		69,307,315		67,554,435
Common stock, par value (in dollars per share)	$ 0.001		$ 0.001		$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	5,000,000		5,000,000		5,000,000
Preferred stock, shares outstanding (in shares)	0		0		0
Preferred stock, issued (in shares)	0		0		0
Preferred stock, par value (in dollars per share)	$ 0.001		$ 0.001		$ 0.001
Fair value of stock options exercised			$ 3.0
Accrual for cash awards	$ 5.1	$ 7.9	10.4	$ 11.6
Stock-based compensation expense	$ 15.1	$ 15.9	$ 29.7	$ 30.6
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 24.76	$ 12.36	$ 25.71	$ 12.25
Dividend yield (percent)	0.00%	0.00%	0.00%	0.00%
Expected life (in years)	5 years	5 years	5 years	5 years
Period used to determine volatility			5 years
Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)	40,067,744		40,067,744
Options term (in years)			10 years
Shares reserved for future issuance	6,000,000.0		6,000,000.0
Unrecognized compensation cost related to novested share-based compensation arrangements	$ 24.4		$ 24.4
Weighted average recognition period of unrecognized compensation cost			2 years 10 months 24 days
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)	2,000,000		2,000,000
Shares reserved for future issuance	800,000		800,000
Incentive Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock available for issuance (up to)	3,368,048		3,368,048
Shares reserved for future issuance	1,200,000		1,200,000
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average recognition period of unrecognized compensation cost			3 years 2 months 12 days
Unrecognized compensation cost related to nonvested share-based compensation arrangements	$ 106.2		$ 106.2
Minimum | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Maximum | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years