Segment Reporting - Segment Revenue and Segment Profit (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting [Line Items]
Segment revenue	$ 531	$ 603	$ 1,118	$ 1,221
Wages and benefits	304	344	626	708
Services and supplies	99	115	210	236
Rent lease and maintenance expense	50	52	99	106
Other operating expense	3	5	6	6
Depreciation and amortization expense	29	31	62	65
Segment expenses	485	547	1,003	1,121
Income (Loss) Before Income Taxes From Continuing Operations	46	56	115	100
Commercial
Segment Reporting [Line Items]
Segment revenue	316	365	677	767
Wages and benefits	214	253	449	523
Services and supplies	42	47	90	101
Rent lease and maintenance expense	35	36	69	74
Other operating expense	1	2	2	2
Depreciation and amortization expense	17	20	38	44
Segment expenses	309	358	648	744
Income (Loss) Before Income Taxes From Continuing Operations	7	7	29	23
Government
Segment Reporting [Line Items]
Segment revenue	215	238	441	454
Wages and benefits	90	91	177	185
Services and supplies	57	68	120	135
Rent lease and maintenance expense	15	16	30	32
Other operating expense	2	3	4	4
Depreciation and amortization expense	12	11	24	21
Segment expenses	176	189	355	377
Income (Loss) Before Income Taxes From Continuing Operations	$ 39	$ 49	$ 86	$ 77