Restricted Cash and Investments - Short-Term Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Short-term investments
Amortized Cost	$ 298,012	$ 674,262
Gross Unrealized Gains	0	0
Gross Unrealized Losses	3,955	9,011
Fair Value (Net Carrying Amount)	294,057	665,251
Allowance for credit loss	298,012	674,262
U.S. Treasury securities
Short-term investments
Amortized Cost	298,012	674,262
Gross Unrealized Gains	0	0
Gross Unrealized Losses	3,955	9,011
Fair Value (Net Carrying Amount)	294,057	665,251
Allowance for credit loss	$ 298,012	$ 674,262

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).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

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- Definition

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).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI https://asc.fasb.org/extlink&oid=126970911&loc=d3e27161-111563

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- Definition

Amortized cost excluding accrued interest, after allowance for credit loss, 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/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI https://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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- Definition

Amount excluding accrued interest, of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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