Note 12 - Stockholders' Equity and Earnings Per Share - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Balance		$ 1,973,304	$ 1,828,539	$ 1,747,778
Total other comprehensive (loss)/income, net of tax		(6,424)	1,204	4,711
Balance		2,121,866	1,973,304	1,828,539
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Reclassification adjustment for equity securities, before tax	[1]	(12,147)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		(11,263)	1,843
Total other comprehensive (loss)/income, pre-tax		(22)	(1,006)
Securities available-for-sale		(11,285)	837
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act, tax		200
Reclassification adjustment for equity securities, tax		(3,591)
Reclassification adjustment for net losses/(gains) included in net income, tax		(3,329)	775
Total other comprehensive (loss)/income, tax		(7)	(423)
Securities available-for-sale		(3,336)	352
Balance		(1,060)	(1,545)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act	[2]	(200)
Reclassification adjustment for equity securities, after tax		(8,556)
Net unrealized (losses)/gains arising during the period, net of tax		7,934	(1,068)
Reclassification adjustment for net losses/(gains) included in net income, net of tax		(15)	(583)
Total other comprehensive (loss)/income, net of tax		(7,949)	485
Balance		(17,765)	(1,060)	(1,545)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		2,165	1,241
Total other comprehensive (loss)/income, pre-tax
Securities available-for-sale		2,165	1,241
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act, tax		315
Reclassification adjustment for net losses/(gains) included in net income, tax		640	522
Total other comprehensive (loss)/income, tax
Securities available-for-sale		640	522
Balance		(1,451)	(2,170)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act	[2]	(315)
Net unrealized (losses)/gains arising during the period, net of tax		(1,525)	(719)
Reclassification adjustment for net losses/(gains) included in net income, net of tax
Total other comprehensive (loss)/income, net of tax		1,525	719
Balance		(241)	(1,451)	(2,170)
AOCI Attributable to Parent [Member]
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		(9,098)	3,084
Total other comprehensive (loss)/income, pre-tax		(22)	(1,006)
Securities available-for-sale		(9,120)	2,078
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act, tax		515
Reclassification adjustment for net losses/(gains) included in net income, tax		(2,689)	1,297
Total other comprehensive (loss)/income, tax		(7)	(423)
Securities available-for-sale		(2,696)	874
Balance		(2,511)	(3,715)	(8,426)
Reclassification adjustment for stranded tax effects of Tax Cuts and Jobs Act		(515)
Net unrealized (losses)/gains arising during the period, net of tax		6,409	(1,787)
Reclassification adjustment for net losses/(gains) included in net income, net of tax		(15)	(583)
Total other comprehensive (loss)/income, net of tax		(6,424)	1,204	4,711
Balance		$ (18,006)	$ (2,511)	$ (3,715)

[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.