Investments - Available-for-sale securities (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale
Amortized Cost	$ 845,509	$ 1,242,933
Gross Unrealized Gains	133	20
Gross Unrealized Losses	(26,202)	(2,688)
Fair Value	819,440	1,240,265
Aggregate fair value of available for sale securities	819,440
Available for sale securities in a continuous unrealized loss position	385,825
Corporate bonds
Debt Securities, Available-for-sale
Amortized Cost	220,537	228,614
Gross Unrealized Losses	(9,004)	(2,232)
Fair Value	211,533	226,382
Aggregate fair value of available for sale securities	819,440
Available for sale securities in a continuous unrealized loss position	385,825
U.S. Treasuries
Debt Securities, Available-for-sale
Amortized Cost	624,972	1,014,319
Gross Unrealized Gains	133	20
Gross Unrealized Losses	(17,198)	(456)
Fair Value	$ 607,907	$ 1,013,883

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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