Lease Obligations (Additional Lease Information) (Narrative) (Details)	3 Months Ended
	Mar. 31, 2021
Lessee, Lease, Description [Line Items]
Finance leases, weighted average remaining lease term (in years)	2 years 6 months
Finance leases, weighted average discount rate, percent	3.70%
Operating leases, weighted average remaining lease term (in years)	3 years 10 months 24 days
Operating leases, weighted average discount rate, percent	3.50%
Minimum [Member] | Equipment Leases [Member]
Lessee, Lease, Description [Line Items]
Leases, renewal term	1 year
Minimum [Member] | Facility Leases [Member]
Lessee, Lease, Description [Line Items]
Leases, renewal term	1 year
Maximum [Member]
Lessee, Lease, Description [Line Items]
Leases, remaining lease terms	8 years
Maximum [Member] | Equipment Leases [Member]
Lessee, Lease, Description [Line Items]
Leases, renewal term	5 years
Maximum [Member] | Facility Leases [Member]
Lessee, Lease, Description [Line Items]
Leases, renewal term	5 years