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Fair Value Measurements (Narrative) (Details) € in Millions, gal in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023 USD ($) € / shares $ / gal	Jun. 30, 2022 USD ($)	Jun. 30, 2023 USD ($) € / shares $ / gal gal	Jun. 30, 2022 USD ($)	Jun. 30, 2023 EUR (€) € / shares $ / gal	Dec. 31, 2022 USD ($)	May 31, 2021 USD ($)
Derivatives Fair Value [Line Items]
Debt instrument, face amount							$ 325,000,000
Fair Value, Inputs, Level 1 [Member]
Derivatives Fair Value [Line Items]
Fair value of debt	$ 271,450,000		$ 271,450,000
Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative underlying hedge percent			80.00%
Derivative, nonmonetary notional amount, volume | gal			8.5
Reclassification of derivative (gains) losses to earnings net of tax	1,434,000	$ (4,719,000)	$ 1,804,000	$ (7,200,000)
Fair value hedge liabilities	$ 1,112,000		$ 1,112,000			$ 638,000
Fuel Hedge Contracts [Member] | Minimum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | $ / gal	2.34		2.34		2.34
Fuel Hedge Contracts [Member] | Maximum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | $ / gal	3.22		3.22		3.22
Foreign Currency Exchange Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Fair value hedge assets	$ 723,000		$ 723,000			831,000
Reclassification of derivative (gains) losses to earnings net of tax	$ (279,000)	$ (241,000)	$ (321,000)
Derivative notional amount | €					€ 26.1
Fair value hedge liabilities						$ 6,000
Foreign Currency Exchange Hedge Contracts [Member] | Minimum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | € / shares	1		1		1
Foreign Currency Exchange Hedge Contracts [Member] | Maximum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | € / shares	1.13		1.13		1.13

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