Consolidated Balance Sheet (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowance for parts and supplies	$ 1,595	$ 795
Preferred stock, par value (in dollars per share)	$ 0.10	$ 0.10
Preferred stock, authorized	10,000,000	10,000,000
Preferred stock, issued	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, outstanding	30,245,000	29,955,000