Revenue from Contracts with Customers - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
Disaggregation of Revenue [Line Items]
Revenues	$ 1,066	$ 960	$ 2,825	$ 2,588
Intersegment sales
Disaggregation of Revenue [Line Items]
Revenues	(21)	(3)	(36)	(9)
ASC \| Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	563	509	1,572	1,414
ASC \| Flexibly Priced
Disaggregation of Revenue [Line Items]
Revenues	76	68	200	210
ASC \| Prime contractor
Disaggregation of Revenue [Line Items]
Revenues	302	298	807	760
ASC \| Subcontractor
Disaggregation of Revenue [Line Items]
Revenues	337	279	965	864
ASC \| Intersegment sales
Disaggregation of Revenue [Line Items]
Revenues	(20)	(3)	(33)	(9)
ASC \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	659	580	1,805	1,633
ASC \| United States
Disaggregation of Revenue [Line Items]
Revenues	558	500	1,516	1,411
ASC \| International
Disaggregation of Revenue [Line Items]
Revenues	81	77	256	213
IMS \| Fixed-price
Disaggregation of Revenue [Line Items]
Revenues	343	359	847	855
IMS \| Flexibly Priced
Disaggregation of Revenue [Line Items]
Revenues	84	24	206	109
IMS \| Prime contractor
Disaggregation of Revenue [Line Items]
Revenues	107	136	223	236
IMS \| Subcontractor
Disaggregation of Revenue [Line Items]
Revenues	320	247	830	728
IMS \| Intersegment sales
Disaggregation of Revenue [Line Items]
Revenues	(1)	0	(3)	0
IMS \| Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	428	383	1,056	964
IMS \| United States
Disaggregation of Revenue [Line Items]
Revenues	411	366	1,005	956
IMS \| International
Disaggregation of Revenue [Line Items]
Revenues	$ 16	$ 17	$ 48	$ 8