Leases (Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease ROU assets, other long term assets	$ 942	$ 764
Operating lease liabilities, current	189	158
Operating lease liabilities, long-term	785	639
Total operating lease liabilities	974	797
Operating lease ROU assets	942	764
Total operating lease liabilities	$ 974	$ 797
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us:gaap_OtherAssetsNoncurrent	us:gaap_OtherAssetsNoncurrent
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us:gaap_AccruedLiabilitiesCurrent	us:gaap_AccruedLiabilitiesCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us:gaap_OtherLiabilitiesNoncurrent	us:gaap_OtherLiabilitiesNoncurrent
Weighted average remaining lease term	7 years	7 years
Weighted average discount rate	2.80%	3.10%