Convertible Senior Notes - Narrative (Details)	1 Months Ended	3 Months Ended				9 Months Ended
	May 31, 2018 USD ($) d $ / shares shares	Sep. 30, 2021 USD ($) option shares	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2021 USD ($) option shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Loss on extinguishment of debt						$ 7,303,000	$ (659,000)
Adjustments to additional paid in capital, equity component of convertible debt		$ 32,000	$ 1,073,000	$ 9,086,000	$ 2,745,000
Adjustments to additional paid-in-capital from warrants						500,000
Payments to unwind warrants						18,400,000
Proceeds from unwinding convertible bond hedges						$ 18,900,000
Number of options under convertible bond hedges | option		598,021				598,021
Convertible Notes | 2023 Convertible Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount outstanding	$ 750,000,000	$ 343,301,000				$ 343,301,000		$ 495,280,000
Interest rate (as a percent)	0.75%
Proceeds from debt, net of issuance costs	$ 733,100,000
Initial conversion rate (shares per $1,000)	0.0040244
Initial conversion price (USD per share) | $ / shares	$ 248.48
Debt issuance costs		16,900,000				16,900,000
Debt premium		13,700,000				13,700,000
Repurchased amount of debt instrument		$ 152,000,000				152,000,000
Repayments of notes						156,000,000
Accrued Interest						300,000
Loss on extinguishment of debt						7,300,000
Increase (decrease) in debt discount						13,700,000
Adjustments to additional paid in capital, equity component of convertible debt						$ 10,200,000
Warrants issued in public offering (shares) | shares	3,018,327	2,559,254				2,559,254
Payments for convertible bond hedges	$ 140,300,000
Warrant exercise price (USD per share) | $ / shares	$ 315.38
Adjustments to additional paid-in-capital from warrants	$ 90,000,000
Convertible Notes | 2023 Convertible Senior Notes | Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Threshold trading days | d	20
Consecutive trading days | d	30
Stock price trigger to classify convertible debt as current (as a percent)	130.00%
Convertible Notes | 2023 Convertible Senior Notes | Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Threshold trading days | d	5
Consecutive trading days | d	10
Maximum threshold of debt trading price trigger (as a percent)	98.00%