Cash and Marketable Securities - Schedule of Restricted Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 207,537	$ 79,449	$ 39,661	$ 77,123
Restricted cash included within other non-current assets	1,500	1,500	1,500	1,500
Total cash, cash equivalents, and restricted cash	$ 209,037	$ 80,949	$ 41,161	$ 78,623