Debt - Debt Discount, Liability, and Equity Allocations of Transaction Costs (Details) - USD ($)		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2020	Aug. 06, 2020	Jul. 07, 2020	Jun. 25, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Debt discount	$ 38,900,000	$ 38,900,000				$ 0
Transaction costs
Total transaction costs	5,500,000	5,500,000				$ 0
Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Debt discount, excluding amortization		39,000,000.0
Amortization of debt discount		(100,000)
Debt discount	38,900,000	38,900,000
Transaction costs
Liability	5,500,000	5,500,000
Equity	1,200,000	1,200,000
Total transaction costs	6,700,000	6,700,000
Convertible Senior Notes Due 2025 | Convertible Debt
Debt Instrument [Line Items]
Debt discount, excluding amortization	200,000
Amortization of debt discount	100,000
Debt discount					$ 42,600,000
Transaction costs
Total transaction costs					1,300,000
Aggregate principal amount of debt					225,000,000
Over-Allotment Option
Debt Instrument [Line Items]
Debt discount	3,600,000	3,600,000
Transaction costs
Liability	500,000	500,000
Equity	100,000	100,000
Total transaction costs	600,000	600,000
Over-Allotment Option | Convertible Debt
Transaction costs
Amortization of transaction costs	100,000
Aggregate principal amount of debt	20,750,000	20,750,000			33,750,000
Over-Allotment Option | Convertible Debt | Subsequent Event
Debt Instrument [Line Items]
Debt discount			$ 3,600,000
Transaction costs
Total transaction costs			$ 100,000	$ 7,300,000
Aggregate principal amount of debt				$ 20,750,000
2025 Notes | Convertible Debt
Debt Instrument [Line Items]
Debt discount					$ 42,600,000
Transaction costs
Liability	6,000,000.0	6,000,000.0
Equity	1,300,000	1,300,000
Total transaction costs	$ 7,300,000	$ 7,300,000