Leases (Summary of Financial Information Associated with Leases) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Assets
Operating lease right-of-use assets	$ 775	$ 688
Total leased assets	1,019	913
Current
Accrued expenses and other liabilities	199	178
Short-term debt and current maturities of long-term debt	$ 46	$ 60
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other liabilities	Accrued expenses and other liabilities
Long-term
Operating lease liabilities	$ 615	$ 549
Long-term debt	93	75
Total lease liabilities	953	862
Property and equipment, net
Assets
Accumulated depreciation	(17)	(11)
Finance lease assets, net	14	16
Sales of rental equipment
Assets
Finance lease, right-of-use asset, before accumulated amortization	323	295
Accumulated depreciation	(93)	(86)
Finance lease assets, net	230	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	$ 23	$ 19