Restructuring Charges - Change in Restructuring Liability (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Restructuring Reserve [Roll Forward]
Restructuring reserve, balance at beginning of period	$ 173
Charges to Earnings	20	$ 5
Cash Paid	(49)
Non-Cash and Other	(5)
Restructuring reserve, balance at end of period	139
Employee termination costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, balance at beginning of period	145
Charges to Earnings	19
Cash Paid	(42)
Non-Cash and Other	0
Restructuring reserve, balance at end of period	122
Asset impairment costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, balance at beginning of period	8
Charges to Earnings	0
Cash Paid	0
Non-Cash and Other	0
Restructuring reserve, balance at end of period	8
Facility exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, balance at beginning of period	0
Charges to Earnings	0
Cash Paid	0
Non-Cash and Other	0
Restructuring reserve, balance at end of period	0
Other exit costs
Restructuring Reserve [Roll Forward]
Restructuring reserve, balance at beginning of period	20
Charges to Earnings	1
Cash Paid	(7)
Non-Cash and Other	(5)
Restructuring reserve, balance at end of period	$ 9