Note 10 - Leasing Activities - Future Minimum Lease Payments Under Capital and Non-cancelable Vehicle Leases (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
2018, Capital Leases	$ 19,819
2018	1,312
2019, Capital Leases	20,499
2019	1,263
2020, Capital Leases	19,037
2020	949
2021, Capital Leases	13,826
2021	502
2022, Capital Leases	10,781
2022	452
Thereafter, Capital Leases	6,735
Thereafter	143
Total minimum lease payments, Capital Leases	90,697
Total minimum lease payments, Operating Leases	4,621
Less amount representing interest, Capital Leases	(7,556)
Present value of net minimum capital lease payments	83,141
Less current portion	(17,119)	$ (14,449)
Obligations under capital leases less current portion	$ 66,022	$ 70,044