Fair Value of Financial Instruments - Unrealized Gains and Losses (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale investments, continuous loss position for less than twelve months	$ 63,473	$ 383,736
Fair value of available-for-sale investments, continuous loss position for twelve months or greater	170,682	285,676
Total fair value of available-for-sale investments, continuous loss position	234,155	669,412
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale investments, continuous loss position for less than 12 months, gross unrealized losses	(354)	(5,923)
Available-for-sale investments, continuous loss position for 12 months or greater, gross unrealized losses	(2,773)	(7,631)
Available-for-sale investments, total gross unrealized losses	(3,127)	(13,554)
Corporate debt securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale investments, continuous loss position for less than twelve months	13,876	307,085
Fair value of available-for-sale investments, continuous loss position for twelve months or greater	132,920	185,467
Total fair value of available-for-sale investments, continuous loss position	146,796	492,552
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale investments, continuous loss position for less than 12 months, gross unrealized losses	(13)	(5,297)
Available-for-sale investments, continuous loss position for 12 months or greater, gross unrealized losses	(1,865)	(4,090)
Available-for-sale investments, total gross unrealized losses	(1,878)	(9,387)
Government debt securities
Continuous unrealized loss position, Fair Value
Fair value of available-for-sale investments, continuous loss position for less than twelve months	49,597	76,651
Fair value of available-for-sale investments, continuous loss position for twelve months or greater	37,762	100,209
Total fair value of available-for-sale investments, continuous loss position	87,359	176,860
Continuous unrealized loss position, Gross Unrealized Losses
Available-for-sale investments, continuous loss position for less than 12 months, gross unrealized losses	(341)	(626)
Available-for-sale investments, continuous loss position for 12 months or greater, gross unrealized losses	(908)	(3,541)
Available-for-sale investments, total gross unrealized losses	$ (1,249)	$ (4,167)