Segment Information and Concentrations - Revenue by Products and Services (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue from External Customer [Line Items]
Total revenue	$ 1,484	$ 1,710	$ 2,987	$ 3,246
Product revenue
Revenue from External Customer [Line Items]
Total revenue	481	664	955	1,203
Professional services and installation services revenue
Revenue from External Customer [Line Items]
Total revenue	189	270	416	508
Recurring revenue, including maintenance, cloud revenue and payments
Revenue from External Customer [Line Items]
Total revenue	814	776	1,616	1,535
Software
Revenue from External Customer [Line Items]
Total revenue	460	496	934	963
Services
Revenue from External Customer [Line Items]
Total revenue	605	622	1,241	1,207
Hardware
Revenue from External Customer [Line Items]
Total revenue	$ 419	$ 592	$ 812	$ 1,076