Segment Information - Depreciation and Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Segment Reporting Information [Line Items]
Depreciation	$ 13	$ 11	$ 37	$ 33
Assets	2,886		2,886		$ 2,956
AST
Segment Reporting Information [Line Items]
Depreciation	5	5	15	14
NC&C
Segment Reporting Information [Line Items]
Depreciation	4	3	10	9
IMS
Segment Reporting Information [Line Items]
Depreciation	4	$ 3	12	$ 10
Operating Segments | AST
Segment Reporting Information [Line Items]
Assets	944		944		862
Operating Segments | NC&C
Segment Reporting Information [Line Items]
Assets	651		651		691
Operating Segments | IMS
Segment Reporting Information [Line Items]
Assets	1,001		1,001		963
Corporate & Eliminations
Segment Reporting Information [Line Items]
Assets	$ 290		$ 290		$ 440