Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Disaggregation of Revenue [Line Items]
Total revenues	$ 681	$ 583
Intersegment Sales
Disaggregation of Revenue [Line Items]
Total revenues	(3)	(7)
AST | Prime contractor
Disaggregation of Revenue [Line Items]
Total revenues	105	85
AST | Subcontractor
Disaggregation of Revenue [Line Items]
Total revenues	113	94
AST | Firm Fixed Price
Disaggregation of Revenue [Line Items]
Total revenues	189	155
AST | Flexibly Priced
Disaggregation of Revenue [Line Items]
Total revenues	29	24
AST | Intersegment Sales
Disaggregation of Revenue [Line Items]
Total revenues	1	4
AST | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	219	183
NC&C | Prime contractor
Disaggregation of Revenue [Line Items]
Total revenues	172	123
NC&C | Subcontractor
Disaggregation of Revenue [Line Items]
Total revenues	90	91
NC&C | Firm Fixed Price
Disaggregation of Revenue [Line Items]
Total revenues	238	195
NC&C | Flexibly Priced
Disaggregation of Revenue [Line Items]
Total revenues	24	19
NC&C | Intersegment Sales
Disaggregation of Revenue [Line Items]
Total revenues	2	3
NC&C | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	264	217
IMS | Prime contractor
Disaggregation of Revenue [Line Items]
Total revenues	44	65
IMS | Subcontractor
Disaggregation of Revenue [Line Items]
Total revenues	157	125
IMS | Firm Fixed Price
Disaggregation of Revenue [Line Items]
Total revenues	170	161
IMS | Flexibly Priced
Disaggregation of Revenue [Line Items]
Total revenues	31	29
IMS | Intersegment Sales
Disaggregation of Revenue [Line Items]
Total revenues	0	0
IMS | Operating Segments
Disaggregation of Revenue [Line Items]
Total revenues	201	190
United States | AST
Disaggregation of Revenue [Line Items]
Total revenues	197	160
United States | NC&C
Disaggregation of Revenue [Line Items]
Total revenues	249	194
United States | IMS
Disaggregation of Revenue [Line Items]
Total revenues	189	185
International | AST
Disaggregation of Revenue [Line Items]
Total revenues	21	19
International | NC&C
Disaggregation of Revenue [Line Items]
Total revenues	13	20
International | IMS
Disaggregation of Revenue [Line Items]
Total revenues	$ 12	$ 5