Note 11 - Income Taxes - Income Tax Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax provision at Federal statutory rate, amount									$ 70,914	$ 104,407	$ 84,770
Tax provision at Federal statutory rate, percent									21.00%	35.00%	35.00%
State income taxes, net of Federal income tax benefit, amount									$ 29,750	$ 20,616	$ 17,250
State income taxes, net of Federal income tax benefit, percent									8.80%	6.90%	7.10%
Deferred taxes write-down due to Tax Cuts and Jobs Act, amount										$ 23,365
Deferred taxes write-down due to Tax Cuts and Jobs Act, percentage										7.80%
Excess deduction for stock option and RSUs, amount									$ (555)	$ (3,146)
Excess deduction for stock option and RSUs									(0.20%)	(1.00%)
Non-taxable bargain purchase gain, amount									$ (71)	$ (1,970)
Non-taxable bargain purchase gain										(0.70%)
Low income housing and other tax credits, amount									$ (34,517)	$ (20,656)	$ (37,901)
Low income housing and other tax credits									(10.20%)	(6.90%)	(15.60%)
Non-deductible stock options expense, amount											$ 3,469
Non-deductible stock options expense											1.40%
Other, net, amount									$ 281	$ (351)	$ (487)
Other, net									0.10%	(0.10%)	(0.20%)
Total income tax expense, amount	$ 17,193	$ 18,698	$ 11,046	$ 18,866	$ 51,166	$ 35,163	$ 15,431	$ 20,505	$ 65,802	$ 122,265	$ 67,101
Total income tax expense									19.50%	41.00%	27.70%