Convertible Senior Notes - Capped Calls (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Capped Calls, initial strike price (in dollars per share)	$ 32.25
Capped Calls, initial cap price (in dollars per share)	$ 38.94
Capped Calls, number of shares covered	4.5
Payment for purchase of capped calls	$ (8,900)	$ 0	$ (8,907)	$ 0
Issuance costs			1,136
Convertible Debt | Convertible Senior Notes At 1.50%, Option Portion
Debt Instrument [Line Items]
Carrying amount of the equity component	$ 33,400	33,350	33,350
Carrying amount of equity component, net of capped calls		$ 23,307	$ 23,307