Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating lease expense	$ 46	$ 40
Variable lease payments not included in the measurement of lease liabilities	20	21
Short-term lease payments not included in the measurement of lease liabilities	7	9
Cash paid for amounts included in the measurement of lease liabilities	42	42
Lease obligations obtained in exchange for right-of-use assets (non-cash)	47	241
Operating lease right of use assets	192	189
Operating lease liabilities - current (in Other current liabilities)	40	35
Operating lease liabilities - noncurrent	163	164
Total operating lease liabilities	$ 203	$ 199
Weighted-average remaining lease term—operating leases (years)	6 years 7 months 2 days	7 years 1 month 13 days
Weighted-average discount rate—operating leases	3.12%	3.67%
2021	$ 46
2022	39
2023	32
2024	27
2025	21
After 2025	57
Total Lease Payments	222
Less: Imputed Interest	(19)
Total rent expense			$ 45
Debt, principal amount	$ 7,250	$ 6,500
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesCurrent	us-gaap:OtherLiabilitiesCurrent
Minimum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	1 year
Maximum
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Term of Contract	14 years