Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Fair Value Disclosures [Line Items]
Gross unrealized losses	$ 0.1
Fair value of convertible senior notes	1,200.0
Domestic Cash and Investments
Fair Value Disclosures [Line Items]
Cash, cash equivalents and restricted cash	$ 960.0		$ 963.4
Minimum
Fair Value Disclosures [Line Items]
Long-term investments maturity period	1 year
Maximum
Fair Value Disclosures [Line Items]
Long-term investments maturity period	2 years
Cumulative effect of adoption of ASC 326 | Accumulated Other Comprehensive Gain (Loss)
Fair Value Disclosures [Line Items]
Gross unrealized losses		$ 0.1