Note 11 - Stockholders' Equity and Earnings Per Share - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Balance		$ 2,121,866	$ 1,973,304	$ 1,828,539
Total other comprehensive (loss)/income, net of tax		20,308	(6,424)	1,204
Balance		2,294,283	2,121,866	1,973,304
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Reclassification adjustment for equity securities, before tax	[1]	0	(12,147)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		33,543	(11,263)
Total other comprehensive (loss)/income, pre-tax		(211)	(22)
Securities available-for-sale		33,332	(11,285)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act, tax	[2]	0	200
Reclassification adjustment for equity securities, tax	[1]	0	(3,591)
Reclassification adjustment for net losses/(gains) included in net income, tax		9,915	(3,329)
Total other comprehensive (loss)/income, tax		(62)	(7)
Securities available-for-sale		9,853	(3,336)
Balance		(17,765)	(1,060)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act	[2]	0	(200)
Reclassification adjustment for equity securities, after tax	[1]	0	(8,556)
Net unrealized (losses)/gains arising during the period, net of tax		(23,628)	7,934
Reclassification adjustment for net losses/(gains) included in net income, net of tax		(149)	(15)
Total other comprehensive (loss)/income, net of tax		23,479	(7,949)
Balance		5,714	(17,765)	(1,060)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		(4,502)	2,165
Total other comprehensive (loss)/income, pre-tax		0	0
Securities available-for-sale		(4,502)	2,165
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act, tax	[2]	0	315
Reclassification adjustment for net losses/(gains) included in net income, tax		(1,331)	640
Total other comprehensive (loss)/income, tax		0	0
Securities available-for-sale		(1,331)	640
Balance		(241)	(1,451)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act	[2]	0	(315)
Net unrealized (losses)/gains arising during the period, net of tax		3,171	(1,525)
Reclassification adjustment for net losses/(gains) included in net income, net of tax		0	0
Total other comprehensive (loss)/income, net of tax		(3,171)	1,525
Balance		(3,412)	(241)	(1,451)
AOCI Attributable to Parent [Member]
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		29,041	(9,098)
Total other comprehensive (loss)/income, pre-tax		(211)	(22)
Securities available-for-sale		28,830	(9,120)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act, tax	[2]	0	515
Reclassification adjustment for net losses/(gains) included in net income, tax		8,584	(2,689)
Total other comprehensive (loss)/income, tax		(62)	(7)
Securities available-for-sale		8,522	(2,696)
Balance		(18,006)	(2,511)	(3,715)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act		0	(515)
Net unrealized (losses)/gains arising during the period, net of tax		(20,457)	6,409
Reclassification adjustment for net losses/(gains) included in net income, net of tax		(149)	(15)
Total other comprehensive (loss)/income, net of tax		20,308	(6,424)	1,204
Balance		$ 2,302	$ (18,006)	$ (2,511)

[1] This amount was recorded as of January 1, 2018 as a result of the adoption of ASU 2016-1.

[2] These amounts were recorded as of January 1, 2018 as a result of the adoption of ASU 2018-2.