Investments - Available-for-sale securities (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale
Amortized Cost	$ 1,355,614	$ 1,242,933
Gross Unrealized Gains	118	20
Gross Unrealized Losses	(22,789)	(2,688)
Fair Value	1,332,943	1,240,265
Corporate bonds
Debt Securities, Available-for-sale
Amortized Cost	200,735	228,614
Gross Unrealized Gains	7
Gross Unrealized Losses	(7,109)	(2,232)
Fair Value	193,633	226,382
U.S. Treasuries
Debt Securities, Available-for-sale
Amortized Cost	1,154,879	1,014,319
Gross Unrealized Gains	111	20
Gross Unrealized Losses	(15,680)	(456)
Fair Value	$ 1,139,310	$ 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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Amount, before tax, of unrealized loss 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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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount of 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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