Note 8 - Leases - Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Amortization of right-of-use assets	$ 31,132	$ 27,213	$ 62,109	$ 54,858
Interest on lease liabilities	1,943	2,152	4,039	3,872
Operating lease cost	272,108	270,040	544,443	540,082
Sublease income	(12,300)	(12,300)	(24,600)	(22,600)
Total lease costs	$ 292,883	$ 287,105	$ 585,991	$ 576,212
Weighted-average remaining lease term - financing leases (in years) (Year)	3 years		3 years
Weighted-average remaining lease term - operating leases (in years) (Year)	14 years 8 months 12 days		14 years 8 months 12 days
Weighted-average discount rate - financing leases	1.95%		1.95%
Weighted-average discount rate - operating leases	5.64%		5.64%