Convertible Senior Notes - Narrative (Details)					1 Months Ended						2 Months Ended			12 Months Ended
	Jan. 28, 2021 USD ($)	Aug. 15, 2019 USD ($)	Dec. 31, 2018 USD ($)	May 22, 2018 USD ($) $ / shares shares	Apr. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Nov. 30, 2018 shares	Jun. 19, 2018 USD ($)	May 31, 2018 trading_day	Aug. 31, 2014 USD ($) day trading_day $ / shares shares	Nov. 30, 2018 USD ($)	Aug. 31, 2018 USD ($)	Apr. 30, 2018 USD ($)	Dec. 31, 2020 USD ($) $ / shares shares	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Debt Instrument [Line Items]
Net change in fair value of derivatives																$ 1,800,000
Warrants issued in public offering (shares) | shares										3,264,643
Exercise price of convertible bond hedge (USD per share) | $ / shares										$ 75.05
Gain (loss) on derivative liabilities																(1,800,000)
Warrant exercise price (USD per share) | $ / shares										$ 125.08				$ 1.50
Value of warrants issued										$ 11,600,000
Warrants settled (shares) | shares							525,000
Deduction to additional paid-in-capital for warrants settled																28,300,000
Payments for repurchase of warrants														$ 0	$ 380,000	30,094,000
Warrants outstanding (shares) | shares														0
Debt issuance costs related to the equity component of convertible debt														$ (3,236,000)
2023 Convertible Senior Notes
Debt Instrument [Line Items]
Value of warrants issued																97,805,000
Convertible Notes
Debt Instrument [Line Items]
Face amount of debt instrument														495,280,000	750,000,000
Total long-term portion of notes payable														442,293,000	638,959,000
Convertible Notes | 2019 Convertible Senior Notes
Debt Instrument [Line Items]
Face amount of debt instrument										245,000,000.0
Net proceeds from debt issuance										$ 239,300,000
Effective rate (as a percent)										5.83%
Convertible debt conversion ratio										0.0133251
Debt conversion price per share (USD per share) | $ / shares										$ 75.05
Interest on debt instrument (as a percent)										0.75%
If-converted value in excess of principal			$ 23,400,000	$ 341,600,000
Increase (decrease) in if-converted value in excess of principal																118,700,000
Notices for conversion						$ 1,000,000.0						$ 195,900,000	$ 21,800,000
Conversion value over the principal amount						$ 500,000					$ 439,600,000		$ 31,600,000
Gain (loss) on extinguishment of debt															(3,200,000)
Repayments of notes		$ 26,300,000
Debt issuance costs related to the liability component of convertible debt		$ 11,900,000
Net change in fair value of derivatives															11,000,000.0	(119,400,000)
Payments for convertible bond hedges										$ 48,100,000
Current derivative asset				340,000,000.0											22,600,000
Gain (loss) on derivative liabilities															(11,000,000.0)	$ 119,400,000
Proceeds from derivative instrument															471,200,000
Convertible Notes | 2019 Convertible Senior Notes | Redemption Period One
Debt Instrument [Line Items]
Number of trading days | trading_day										20
Number of consecutive trading days | trading_day										30
Stock price trigger to classify convertible debt as current (as a percent)										130.00%
Convertible Notes | 2019 Convertible Senior Notes | Redemption Period Two
Debt Instrument [Line Items]
Number of trading days | day										5
Number of consecutive trading days | trading_day										10
Maximum threshold of debt trading price trigger (as a percent)										98.00%
Convertible Notes | 2023 Convertible Senior Notes
Debt Instrument [Line Items]
Face amount of debt instrument				750,000,000
Net proceeds from debt issuance				$ 733,100,000
Convertible debt conversion ratio									0.0040244
Debt conversion price per share (USD per share) | $ / shares				$ 248.48
Interest on debt instrument (as a percent)				0.75%
Debt issuance costs related to the liability component of convertible debt				$ 13,700,000
Warrants issued in public offering (shares) | shares				3,018,327
Payments for convertible bond hedges				$ 140,300,000
Warrant exercise price (USD per share) | $ / shares				$ 315.38
Value of warrants issued				$ 90,000,000.0
Fair value of the conversion option derivative liability				144,000,000.0
Increase (decrease) in derivative liabilities								$ 13,500,000							7,500,000
Debt issuance costs				$ 16,900,000
Debt issuance costs related to the equity component of convertible debt														(3,200,000)	3,200,000
Repurchased face amount of debt instrument					$ 234,400,000									254,700,000
Repayments of senior debt					203,800,000									222,800,000
Accrued interest on repurchased debt					$ 600,000									600,000
Loss on repurchase of debt instrument														2,500,000
Reduction in debt discount														$ 35,000,000.0
Increase (decrease) in derivative assets															19,200,000
Convertible Notes | 2023 Convertible Senior Notes | Subsequent Event
Debt Instrument [Line Items]
Repurchased face amount of debt instrument	$ 20,300,000
Repayments of senior debt	19,100,000
Accrued interest on repurchased debt	$ 100,000
Convertible Notes | 2023 Convertible Senior Notes | Redemption Period One
Debt Instrument [Line Items]
Number of trading days | trading_day									20
Number of consecutive trading days | trading_day									30
Stock price trigger to classify convertible debt as current (as a percent)									130.00%
Convertible Notes | 2023 Convertible Senior Notes | Redemption Period Two
Debt Instrument [Line Items]
Number of trading days | trading_day									5
Number of consecutive trading days | trading_day									10
Maximum threshold of debt trading price trigger (as a percent)									98.00%
Other Expense | Convertible Notes | 2019 Convertible Senior Notes
Debt Instrument [Line Items]
Net change in fair value of derivatives															10,200,000
Gain (loss) on derivative liabilities															$ (10,200,000)