Available For Sale Securities - Continuous Unrealized Loss Position (Details) $ in Thousands	Jun. 30, 2020 USD ($)
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Unrealized loss for less than 12 months, gross unrealized losses	$ (9)
Unrealized loss for less than 12 months, estimated fair value	49,943
Unrealized loss for 12 months or more, gross unrealized losses	0
Unrealized loss for 12 months or more, estimated fair value	0
Total, gross unrealized losses	(9)
Total, estimated fair value	49,943
U.S. government debt securities
Debt Securities, Available-for-sale, Unrealized Loss Position [Line Items]
Unrealized loss for less than 12 months, gross unrealized losses	(9)
Unrealized loss for less than 12 months, estimated fair value	49,943
Unrealized loss for 12 months or more, gross unrealized losses	0
Unrealized loss for 12 months or more, estimated fair value	0
Total, gross unrealized losses	(9)
Total, estimated fair value	$ 49,943