Notes Payable - Capped Calls (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	May 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Capped calls
Net cost to purchase the transactions		$ 0	$ 58,465	$ 0
Capped calls
Capped calls
Initial strike price (in dollars per share)	$ 70.90
Initial cap price (in dollars per share)	$ 105.04
Number of shares covered	7,757,172
Net cost to purchase the transactions	$ 58,500