Debt (Details)	1 Months Ended	12 Months Ended
	Aug. 31, 2019 USD ($) day $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($) $ / shares	Dec. 31, 2017 USD ($)	Aug. 31, 2014 USD ($)
Debt Instrument [Line Items]
Proceeds from the issuance of convertible senior notes, net of issuance costs		$ 335,899,000	$ 0	$ 0
Line of Credit | Silicon Valley Bank
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 15,000,000.0
Convertible debt | 1.125% Convertible Senior Notes, Due 2026
Debt Instrument [Line Items]
Face amount of debt issued	$ 345,000,000.0
Stated interest percentage	1.125%
Proceeds from the issuance of convertible senior notes, net of issuance costs	$ 335,900,000
Conversion ratio	0.0124756
Conversion price (in dollars per share) | $ / shares	$ 80.16
Threshold number of trading days (day) | day	20
Threshold number of consecutive trading days (day) | day	30
Threshold percentage of stock price trigger	130.00%
Redemption price, percentage	100.00%
Effective interest percentage	4.30%
Equity component, gross amount	$ 60,100,000
Issuance costs attributable to the liability component	7,500,000
Issuance costs attributable to the equity component	1,600,000
Convertible debt | 1.125% Convertible Senior Notes, Due 2026, Over-Allotment option
Debt Instrument [Line Items]
Face amount of debt issued	$ 45,000,000.0
Class A Common Stock
Debt Instrument [Line Items]
Common stock, par value (in dollars per share) | $ / shares	$ 0.001	$ 0.001	$ 0.001
Debt conversion terms one | Convertible debt | 1.125% Convertible Senior Notes, Due 2026
Debt Instrument [Line Items]
Threshold number of trading days (day) | day	20
Threshold number of consecutive trading days (day) | day	30
Threshold percentage of stock price trigger	130.00%
Debt conversion terms two | Convertible debt | 1.125% Convertible Senior Notes, Due 2026
Debt Instrument [Line Items]
Threshold number of trading days (day) | day	5
Threshold number of consecutive trading days (day) | day	10
Threshold percentage of stock trading price	98.00%