Leases (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Leases [Abstract]
Operating Lease Expense	$ 115	$ 108
short term leases and variable leases costs	35	35
Operating Lease Payments	81	73
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	96	$ 65
Operating Lease, Right-of-Use Asset	$ 1,242		$ 1,214
Included within other noncurrent assets	us-gaap:OtherAssets		us-gaap:OtherAssets
Operating lease liabilities	$ 245		$ 235
Current portion included within accounts payable and accrued liabilities	us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent		us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent
Noncurrent portion of operating lease liability	$ 1,128		$ 1,110
Long-term portion included within other long-term liabilities	OTHER LONG-TERM LIABILITIES		OTHER LONG-TERM LIABILITIES
Total Operating Lease Liability	$ 1,373		$ 1,345
Weighted average remaining operating lease term (in years)	6 years 2 months 12 days		6 years 4 months 24 days
Weighted average discount rate - operating leases (percentage)	3.70%		3.90%
Finance Lease Liabilities	$ 64		$ 63
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
Nine months ended December 31, 2021	237
2022	297
2023	273
2024	230
2025	182
Thereafter	386
Undiscounted lease cash flow commitments	1,605
Reconciling impact from discounting	$ (232)