Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Revenues	$ 913	$ 829	$ 1,759	$ 1,628
Intersegment sales
Disaggregation of Revenue [Line Items]
Revenues	(7)	(3)	(15)	(6)
ASC \| Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	518	468	1,009	905
ASC \| Flexibly Priced
Disaggregation of Revenue [Line Items]
Revenues	63	71	124	142
ASC \| Prime contractor
Disaggregation of Revenue [Line Items]
Revenues	244	238	505	462
ASC \| Subcontractor
Disaggregation of Revenue [Line Items]
Revenues	337	301	628	585
ASC \| Intersegment sales
Disaggregation of Revenue [Line Items]
Revenues	(6)	(3)	(13)	(6)
ASC \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	587	542	1,146	1,053
ASC \| United States
Disaggregation of Revenue [Line Items]
Revenues	487	465	958	911
ASC \| International
Disaggregation of Revenue [Line Items]
Revenues	94	74	175	136
IMS \| Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	262	242	504	496
IMS \| Flexibly Priced
Disaggregation of Revenue [Line Items]
Revenues	70	48	122	85
IMS \| Prime contractor
Disaggregation of Revenue [Line Items]
Revenues	54	54	116	100
IMS \| Subcontractor
Disaggregation of Revenue [Line Items]
Revenues	278	236	510	481
IMS \| Intersegment sales
Disaggregation of Revenue [Line Items]
Revenues	(1)	0	(2)	0
IMS \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	333	290	628	581
IMS \| United States
Disaggregation of Revenue [Line Items]
Revenues	317	296	594	590
IMS \| International
Disaggregation of Revenue [Line Items]
Revenues	$ 15	$ (6)	$ 32	$ (9)