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Fair Value Measurements (Narrative) (Details) € in Millions, gal in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023 USD ($) € / shares $ / gal	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) € / shares $ / gal gal	Sep. 30, 2022 USD ($)	Sep. 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	$ 266,565,000		$ 266,565,000
Fuel Hedge Contracts [Member]
Derivatives Fair Value [Line Items]
Derivative underlying hedge percent			80.00%
Derivative, nonmonetary notional amount, volume | gal			12.6
Reclassification of derivative (gains) losses to earnings net of tax	(297,000)	$ (2,358,000)	$ 1,507,000	$ (9,558,000)
Fair value hedge liabilities	$ 2,868,000		$ 2,868,000			$ 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	$ 374,000		$ 374,000			831,000
Reclassification of derivative (gains) losses to earnings net of tax	$ (198,000)	$ (196,000)	$ (519,000)	$ (196,000)
Derivative notional amount | €					€ 23.7
Fair value hedge liabilities						$ 6,000
Foreign Currency Exchange Hedge Contracts [Member] | Minimum [Member]
Derivatives Fair Value [Line Items]
Fixed price range | € / shares	1.01		1.01		1.01
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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