Accounting Policies - Leases (Details)	3 Months Ended
	Mar. 31, 2019
Minimum | Equipment
Lessee, Lease, Description [Line Items]
Lessee, Operating and Finance Lease, Term of Contract	2 years
Minimum | Property
Lessee, Lease, Description [Line Items]
Lessee, Operating and Finance Lease, Term of Contract	2 years
Maximum | Equipment
Lessee, Lease, Description [Line Items]
Lessee, Operating and Finance Lease, Term of Contract	10 years
Maximum | Property
Lessee, Lease, Description [Line Items]
Lessee, Operating and Finance Lease, Term of Contract	20 years