Long-Term Debt (Narrative) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($)
Debt Instrument [Line Items]
Long-term debt	$ 168,332
Fixed rate debt	24,832
Variable rate debt	143,500
KeyBank Credit Facility [Member]
Debt Instrument [Line Items]
Variable rate debt	118,114
Wells Fargo [Member]
Debt Instrument [Line Items]
Variable rate debt	25,386
OSK X, LLC 1 [Member]
Debt Instrument [Line Items]
Fixed rate debt	13,199
Held For Use [Member]
Debt Instrument [Line Items]
Long-term debt	$ 168,332
Weighted average term	2 years 1 month 6 days
Weighted average interest	3.79%
Fixed rate debt	$ 24,832
Fixed rate, weighted average term	2 years 3 months 18 days
Fixed rate, weighted average interest	4.09%
Variable rate debt	$ 143,500
Variable rate, weighted average term	2 years
Variable rate, weighted average interest	3.74%