Short-Term Investments (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 130,178	$ 129,741
Gross Unrealized gain (Loss)	(160)	(19)
Estimated Fair Value	130,018	129,722
Municipal bonds and notes
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	999	6,001
Gross Unrealized gain (Loss)	0	(1)
Estimated Fair Value	999	6,000
Zero coupon bonds
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	128,649	123,210
Gross Unrealized gain (Loss)	(160)	(18)
Estimated Fair Value	128,489	123,192
Certificates of deposit
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	530	530
Gross Unrealized gain (Loss)	0	0
Estimated Fair Value	$ 530	$ 530

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).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Section 50
-Paragraph 2
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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
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-Section 45
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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), classified as current.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-URI http://asc.fasb.org/extlink&oid=124258926&loc=SL82898722-210454

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