Leases (Narrative) (Details) - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Weighted average remaining lease term			10 years
Weighted average discount rate			2.80%
Operating leases not yet commenced, future minimum lease payments			$ 7.4
Rent expense under operating leases	$ 1.3	$ 1.1
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