Liabilities - Convertible Senior Notes (Details)					3 Months Ended	6 Months Ended
	Nov. 17, 2020 USD ($) $ / shares	May 18, 2020 USD ($) $ / shares	May 13, 2020 USD ($) $ / shares	Jan. 10, 2017 USD ($) $ / shares	Jun. 30, 2021 D	Jun. 30, 2021 USD ($) D
Capped Call Transactions
Debt
Aggregate price of capped call transaction			$ 10,300,000
Cap price of the capped call transactions (in dollars per share) | $ / shares			$ 18.46
Convertible Notes - 2023, 2025 and 2027
Debt
Multiples of principal holders may convert						1,000
Minimum threshold period | D						20
Consecutive trading days | D					30	30
Stock price trigger (as a percent)					130.00%	130.00%
Trading days | D						5
Number of consecutive business days						5 days
Maximum percentage of common stock conversion						98.00%
2023 Notes
Debt
Conversion rate				0.0249800
Conversion price (in dollars per share) | $ / shares				$ 40.03
Measurement input				0.070
Long-term Debt, Measurement Input				us-gaap:MeasurementInputDiscountRateMember
Debt discount				$ 72,500,000
Transaction costs				9,200,000
Transaction costs allocated to the equity component				$ 1,900,000
2025 Notes
Debt
Conversion rate	0.0416667
Conversion price (in dollars per share) | $ / shares	$ 24.00
Measurement input	0.080
Long-term Debt, Measurement Input	us-gaap:MeasurementInputDiscountRateMember
Debt discount	$ 21,000,000.0
Transaction costs	1,900,000
Transaction costs allocated to the equity component	$ 300,000
2027 Notes
Debt
Conversion rate		0.0715372
Conversion price (in dollars per share) | $ / shares		$ 13.98
Measurement input		0.091
Long-term Debt, Measurement Input		us-gaap:MeasurementInputDiscountRateMember
Debt discount		$ 34,200,000
Transaction costs		3,100,000
Transaction costs allocated to the equity component		$ 800,000