Fair Value Measurements (Adjustments Reclassified from Accumulated Balances Other Comprehensive Income (Loss) to Earnings) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Derivative Instruments Gain Loss [Line Items]
Costs of contract revenues	$ 114,768	$ 138,947	$ 260,677	$ 300,241
Other expense (income)	2,024	(1,120)	2,251	(1,525)
Income tax (provision) benefit	(796)	853	(5)	(2,432)
Net income (loss)	1,733	(4,033)	(1,498)	7,024
Accumulated Gain Loss Net Cash Flow Hedge Parent [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments Gain Loss [Line Items]
Income tax (provision) benefit	390	(1,594)	502	(2,432)
Net income (loss)	(1,156)	4,719	(1,487)	7,200
Fuel Hedge Contracts [Member] | Accumulated Gain Loss Net Cash Flow Hedge Parent [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments Gain Loss [Line Items]
Costs of contract revenues	1,918	$ (6,313)	2,413	$ (9,632)
Foreign Currency Exchange Hedge Contracts [Member] | Accumulated Gain Loss Net Cash Flow Hedge Parent [Member] | Reclassification Out of Accumulated Other Comprehensive Income [Member]
Derivative Instruments Gain Loss [Line Items]
Other expense (income)	$ 372		$ 424