Note 10 - Leasing Activities (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Guaranteed Residual Value Under Capital Lease Arrangements	$ 38,000,000
Land and Building [Member]
Operating Leases, Rent Expense, Total	10,700,000	$ 9,500,000	$ 10,300,000
Vehicle Leases as Lessee 1 [Member]
Operating Leases, Rent Expense, Total	2,500,000	900,000	1,300,000
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals	72,800,000
Vehicle Leases as Lessor [Member]
Operating Leases, Income Statement, Minimum Lease Revenue	209,300,000	187,400,000	182,100,000
Operating Leases, Income Statement, Contingent Revenue	30,000,000	29,000,000	$ 27,800,000
Property Subject to or Available for Operating Lease, Net, Total	576,000,000	584,400,000
Property Subject to or Available for Operating Lease, Accumulated Depreciation	338,700,000	$ 310,500,000
Minimum [Member] | Land and Building [Member]
Monthly Rental Payment Operating Lease	$ 275
Minimum [Member] | Vehicle Leases as Lessee 1 [Member]
Lease Term	1 year
Minimum [Member] | Vehicle Leases as Lessor [Member]
Lease Term	1 year
Maximum [Member] | Land and Building [Member]
Monthly Rental Payment Operating Lease	$ 38,091
Maximum [Member] | Vehicle Leases as Lessee 1 [Member]
Lease Term	10 years
Maximum [Member] | Vehicle Leases as Lessor [Member]
Lease Term	10 years