Fair Value Measurements - Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Fair Value Measurements
Available for sale securities	$ 132,349	$ 170,531
Investments in U.S. Treasury securities
Fair Value Measurements
Available for sale securities	21,646	27,423
Investments in corporate debt securities
Fair Value Measurements
Available for sale securities	86,067	109,129
Investments in U.S. government agency securities
Fair Value Measurements
Available for sale securities	9,768	9,669
Asset-backed securities
Fair Value Measurements
Available for sale securities	9,870	19,297
Investments in supranational securities
Fair Value Measurements
Available for sale securities	4,998	5,013
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Investments in money market funds*
Fair Value Measurements
Investments	461,564	475,689
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Investments in U.S. Treasury securities
Fair Value Measurements
Available for sale securities	21,646	27,423
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Investments in corporate debt securities
Fair Value Measurements
Available for sale securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Investments in U.S. government agency securities
Fair Value Measurements
Available for sale securities		0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Asset-backed securities
Fair Value Measurements
Available for sale securities	0	0
Recurring basis | Quoted prices in active markets for identical assets (Level 1) | Investments in supranational securities
Fair Value Measurements
Available for sale securities	0	0
Recurring basis | Significant other observable inputs (Level 2) | Investments in money market funds*
Fair Value Measurements
Investments	0	0
Recurring basis | Significant other observable inputs (Level 2) | Investments in U.S. Treasury securities
Fair Value Measurements
Available for sale securities	0	0
Recurring basis | Significant other observable inputs (Level 2) | Investments in corporate debt securities
Fair Value Measurements
Available for sale securities	86,067	109,129
Recurring basis | Significant other observable inputs (Level 2) | Investments in U.S. government agency securities
Fair Value Measurements
Available for sale securities	9,768	9,669
Recurring basis | Significant other observable inputs (Level 2) | Asset-backed securities
Fair Value Measurements
Available for sale securities	9,870	19,297
Recurring basis | Significant other observable inputs (Level 2) | Investments in supranational securities
Fair Value Measurements
Available for sale securities	4,998	5,013
Recurring basis | Significant unobservable inputs (Level 3) | Investments in money market funds*
Fair Value Measurements
Investments	0	0
Recurring basis | Significant unobservable inputs (Level 3) | Investments in U.S. Treasury securities
Fair Value Measurements
Available for sale securities	0	0
Recurring basis | Significant unobservable inputs (Level 3) | Investments in corporate debt securities
Fair Value Measurements
Available for sale securities	0	0
Recurring basis | Significant unobservable inputs (Level 3) | Investments in U.S. government agency securities
Fair Value Measurements
Available for sale securities		0
Recurring basis | Significant unobservable inputs (Level 3) | Asset-backed securities
Fair Value Measurements
Available for sale securities	0	0
Recurring basis | Significant unobservable inputs (Level 3) | Investments in supranational securities
Fair Value Measurements
Available for sale securities	$ 0	$ 0