Note 10 - Leasing Activities (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Leases, Rent Expense	$ 183,091,000	$ 182,040,000	$ 176,891,000
Operating Leases, Future Minimum Payments Due, Future Minimum Sublease Rentals	71,000,000
Land and Building [Member]
Operating Leases, Rent Expense	9,500,000	10,300,000	11,800,000
Vehicle Leases as Lessee 1 [Member]
Guaranteed Residual Value Under Capital Lease Arrangements	37,000,000
Operating Leases, Rent Expense	900,000	1,300,000	2,400,000
Vehicle Leases as Lessor [Member]
Operating Leases, Income Statement, Minimum Lease Revenue	187,400,000	182,100,000	175,000,000
Operating Leases, Income Statement, Contingent Revenue	29,000,000	27,800,000	$ 27,400,000
Property Subject to or Available for Operating Lease, Net	584,400,000	570,100,000
Property Subject to or Available for Operating Lease, Accumulated Depreciation	310,500,000	262,600,000
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		$ 46,479
Maximum [Member] | Vehicle Leases as Lessee 1 [Member]
Lease Term	10 years
Maximum [Member] | Vehicle Leases as Lessor [Member]
Lease Term	10 years