Investments - Available-for-sale securities (Details) $ in Thousands	Jun. 30, 2021 USD ($)
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,244,618
Gross Unrealized Gains	304
Gross Unrealized Losses	(2,201)
Fair Value	1,242,721
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	707,022
Gross Unrealized Gains	51
Gross Unrealized Losses	(1,989)
Fair Value	705,084
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	329,471
Gross Unrealized Gains	253
Gross Unrealized Losses	(2)
Fair Value	329,722
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	27,460
Gross Unrealized Losses	(6)
Fair Value	27,454
U.S. Treasuries
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	170,672
Gross Unrealized Losses	(195)
Fair Value	170,477
Municipal debt
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,993
Gross Unrealized Losses	(9)
Fair Value	$ 9,984

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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