Leases (Narrative) (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Lessor, operating lease assets	$ 1.0	$ 1.1
Lessor, accumulated depreciation	$ 0.2	$ 0.3
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract	1 year
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, term of contract	47 years
Lease, renewal term	99 years