Segment Information and Concentrations - Revenue by Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Total revenue	$ 1,589	$ 1,783	$ 4,576	$ 5,029
Recurring revenue
Revenue from External Customer [Line Items]
Total revenue	848	806	2,464	2,357
All other products and services
Revenue from External Customer [Line Items]
Total revenue	741	977	2,112	2,672
Software
Revenue from External Customer [Line Items]
Total revenue	468	512	1,402	1,475
Services
Revenue from External Customer [Line Items]
Total revenue	655	640	1,896	1,847
Hardware
Revenue from External Customer [Line Items]
Total revenue	$ 466	$ 631	$ 1,278	$ 1,707