Lease Accounting (Narrative) (Details)	3 Months Ended
	Mar. 31, 2020 contract site
Lessee, Lease, Description [Line Items]
Number of leases with restrictive covenants | site	102
Minimum
Lessee, Lease, Description [Line Items]
Remaining lease term	1 year
Lease renewal term	5 years
Maximum
Lessee, Lease, Description [Line Items]
Remaining lease term	20 years
Lease renewal term	20 years
Land
Lessee, Lease, Description [Line Items]
Number of leases	217
Terminal
Lessee, Lease, Description [Line Items]
Number of leases	1
Hangar
Lessee, Lease, Description [Line Items]
Number of leases	1