Investments - Schedule of Investments' Gross Unrealized Loss and Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	$ 18,916	$ 2,803
Unrealized Losses, Less than 12 Months	(164)	(11)
Fair Value, 12 Months or More	969	0
Unrealized Losses, 12 Months or More	(31)	0
Fair Value	19,885	2,803
Unrealized Losses	(195)	(11)
U.S. Treasury securities, obligations of U.S. Government agencies and municipalities
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	15,987	1,995
Unrealized Losses, Less than 12 Months	(141)	(5)
Fair Value, 12 Months or More	969	0
Unrealized Losses, 12 Months or More	(31)	0
Fair Value	16,956	1,995
Unrealized Losses	(172)	(5)
Corporate debt
Debt Securities, Available-for-sale [Line Items]
Fair Value, Less than 12 Months	2,929	808
Unrealized Losses, Less than 12 Months	(23)	(6)
Fair Value, 12 Months or More	0	0
Unrealized Losses, 12 Months or More	0	0
Fair Value	2,929	808
Unrealized Losses	$ (23)	$ (6)