Note 8 - Leases - Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Amortization of right-of-use assets	$ 38,381	$ 27,226	$ 100,490	$ 82,084
Interest on lease liabilities	1,901	2,138	5,940	6,010
Operating lease cost	273,272	270,042	817,715	810,124
Sublease income	(12,300)	(10,300)	(36,900)	(32,900)
Total lease costs	$ 301,254	$ 289,106	$ 887,245	$ 865,318
Weighted-average remaining lease term - financing leases (in years) (Year)	3 years 7 months 6 days		3 years 7 months 6 days
Weighted-average remaining lease term - operating leases (in years) (Year)	14 years 6 months		14 years 6 months
Weighted-average discount rate - financing leases	1.34%		1.34%
Weighted-average discount rate - operating leases	5.66%		5.66%