Segment Information - Revenues and Intersegment Revenues (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Segment Reporting Information [Line Items]
Revenue	$ 681	$ 583
Operating Segments | AST
Segment Reporting Information [Line Items]
Revenue	219	183
Operating Segments | NC&C
Segment Reporting Information [Line Items]
Revenue	264	217
Operating Segments | IMS
Segment Reporting Information [Line Items]
Revenue	201	190
Corporate & Eliminations
Segment Reporting Information [Line Items]
Revenue	(3)	(7)
Corporate & Eliminations | AST
Segment Reporting Information [Line Items]
Revenue	1	4
Corporate & Eliminations | NC&C
Segment Reporting Information [Line Items]
Revenue	2	3
Corporate & Eliminations | IMS
Segment Reporting Information [Line Items]
Revenue	$ 0	$ 0