Leases (Summary of Financial Information Associated with Leases) (Details) - USD ($) $ in Millions	Jun. 30, 2021	Dec. 31, 2020
Assets
Operating lease right-of-use assets	$ 781	$ 688
Total leased assets	1,019	913
Current
Accrued expenses and other liabilities	192	178
Short-term debt and current maturities of long-term debt	$ 48	$ 60
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesAndOtherLiabilities	us-gaap:AccruedLiabilitiesAndOtherLiabilities
Long-term
Operating lease liabilities	$ 630	$ 549
Long-term debt	89	75
Total lease liabilities	959	862
Property and equipment, net
Assets
Accumulated depreciation	(16)	(11)
Finance lease assets, net	13	16
Sales of rental equipment
Assets
Finance lease, right-of-use asset, before accumulated amortization	313	295
Accumulated depreciation	(88)	(86)
Finance lease assets, net	225	209
Non-rental vehicles
Assets
Finance lease, right-of-use asset, before accumulated amortization	8	8
Buildings
Assets
Finance lease, right-of-use asset, before accumulated amortization	$ 21	$ 19