Leases (Narrative) (Details) $ in Billions	Dec. 31, 2020 USD ($)
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term	9 years
Weighted average discount rate	2.60%
Operating leases not yet commenced, future minimum lease payments	$ 8.0
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, non-cancelable lease term	1 year
Finance lease, non-cancelable lease term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, non-cancelable lease term	25 years
Finance lease, non-cancelable lease term	25 years