Fair Value of Financial Instruments - Assumptions - Convertible Note Hedges (Details)	Jun. 30, 2020 Y $ / shares	Dec. 31, 2019 Y $ / shares
Fair Value of Financial Instruments
Derivative asset, valuation technique	us-gaap:ValuationTechniqueOptionPricingModelMember	us-gaap:ValuationTechniqueOptionPricingModelMember
Measurement Input, Risk Free Interest Rate
Fair Value of Financial Instruments
Derivative asset, measurement input	0.002	0.016
Measurement Input, Expected Term
Fair Value of Financial Instruments
Derivative asset, measurement input | Y	2.0	2.5
Measurement Input, Share Price
Fair Value of Financial Instruments
Derivative asset, measurement input	10.32	13.31
Measurement Input, Exercise Price
Fair Value of Financial Instruments
Derivative asset, measurement input	14.51	14.51
Measurement Input, Price Volatility
Fair Value of Financial Instruments
Derivative asset, measurement input	0.544	0.491
Measurement Input, Expected Dividend Rate
Fair Value of Financial Instruments
Derivative asset, measurement input	0	0