Fair Value Measurements - Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Assets:
Available-for-sale securities	$ 129,722	$ 29,528
Short-term investments	129,722	29,528
Municipal bonds and notes
Assets:
Available-for-sale securities	6,000	28,998
Zero coupon bonds
Assets:
Available-for-sale securities	123,192
Certificates of deposit
Assets:
Available-for-sale securities	530	530
Fair value measured on recurring basis \| Municipal bonds and notes
Assets:
Available-for-sale securities	6,000	28,998
Fair value measured on recurring basis \| Zero coupon bonds
Assets:
Available-for-sale securities	123,192
Fair value measured on recurring basis \| Certificates of deposit
Assets:
Short-term investments	530	530
Fair value measured on recurring basis \| Commodity swap contracts
Assets:
Derivative assets		5,648
Liabilities:
Derivative liabilities	4,383
Fair value measured on recurring basis \| Embedded derivatives
Assets:
Derivative assets	6,776	791
Liabilities:
Derivative liabilities		556
Fair value measured on recurring basis \| Level 2 \| Municipal bonds and notes
Assets:
Available-for-sale securities	6,000	28,998
Fair value measured on recurring basis \| Level 2 \| Zero coupon bonds
Assets:
Available-for-sale securities	123,192
Fair value measured on recurring basis \| Level 2 \| Certificates of deposit
Assets:
Short-term investments	530	530
Fair value measured on recurring basis \| Level 3 \| Commodity swap contracts
Assets:
Derivative assets		5,648
Liabilities:
Derivative liabilities	4,383
Fair value measured on recurring basis \| Level 3 \| Embedded derivatives
Assets:
Derivative assets	$ 6,776	791
Liabilities:
Derivative liabilities		$ 556

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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.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

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