Segment Reporting - Segment Revenue and Segment Profit (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Segment revenue	$ 723	$ 751
Wages and benefits	386	425
Services and supplies	174	172
Rent lease and maintenance expense	61	67
Other operating expense	5	3
Depreciation and amortization expense	39	42
Segment expenses	665	709
Income (Loss) Before Income Taxes	58	42
Commercial
Segment Reporting Information [Line Items]
Segment revenue	361	402
Wages and benefits	236	270
Services and supplies	48	54
Rent lease and maintenance expense	34	38
Other operating expense	1	0
Depreciation and amortization expense	20	24
Segment expenses	339	386
Income (Loss) Before Income Taxes	22	16
Government
Segment Reporting Information [Line Items]
Segment revenue	226	216
Wages and benefits	87	95
Services and supplies	63	66
Rent lease and maintenance expense	15	16
Other operating expense	2	1
Depreciation and amortization expense	12	10
Segment expenses	179	188
Income (Loss) Before Income Taxes	47	28
Transportation
Segment Reporting Information [Line Items]
Segment revenue	136	133
Wages and benefits	63	60
Services and supplies	63	52
Rent lease and maintenance expense	12	13
Other operating expense	2	2
Depreciation and amortization expense	7	8
Segment expenses	147	135
Income (Loss) Before Income Taxes	$ (11)	$ (2)