Restructuring Restructuring - Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
2016 Restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 8	$ 30	$ 82
Organizational restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring charges		55	$ 4
Organizational restructuring | Minimum
Restructuring Cost and Reserve [Line Items]
Restructuring expenses, expected cost	250
Organizational restructuring | Maximum
Restructuring Cost and Reserve [Line Items]
Restructuring expenses, expected cost	300
Continuing Operations | Organizational restructuring
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 201	$ 49