Marketable Securities - Summary of Investments (Details) $ in Thousands	Dec. 31, 2019 USD ($) security	Dec. 31, 2018 USD ($) security
Marketable securities available-for-sale
Amortization Cost	$ 121,103	$ 60,584
Gross Unrealized Gains	39
Gross Unrealized Losses	(2)	(8)
Estimated Fair Value	121,140	60,576
Aggregate fair value of marketable securities with unrealized losses position for less than a year	$ 19,600	$ 60,600
Number of investments in an unrealized loss position for less than a year | security	3	16
U.S. Treasury obligations
Marketable securities available-for-sale
Amortization Cost	$ 121,103	$ 60,584
Gross Unrealized Gains	39
Gross Unrealized Losses	(2)	(8)
Estimated Fair Value	$ 121,140	$ 60,576