Note 19 - Stockholders' Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Balance		$ 2,199,297	$ 2,064,836	$ 2,121,866	$ 1,973,304
Total other comprehensive (loss)/income, net of tax		525	(862)	17,173	(12,198)
Balance		2,245,894	2,116,777	2,245,894	2,116,777
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Net unrealized (losses)/gains arising during the period, pre-tax		1,750	(3,603)	30,119	(23,854)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		(121)	(14)	(108)	(14)
Total other comprehensive (loss)/income, pre-tax		1,871	(3,589)	30,227	(23,840)
Net unrealized (losses)/gains arising during the period, tax		517	(1,065)	8,903	(7,051)
Reclassification adjustment for net losses/(gains) included in net income, tax		(36)	(4)	(32)	(4)
Total other comprehensive (loss)/income, tax		553	(1,061)	8,935	(7,047)
Reclassification adjustment for stranded tax effects of Tax Cuts and Job Act, tax	[1]			0	200
Balance		2,209	(24,084)	(17,765)	(1,060)
Net unrealized (losses)/gains arising during the period, net of tax		1,233	(2,538)	21,216	(16,803)
Reclassification adjustment for net losses/(gains) included in net income, net of tax		(85)	(10)	(76)	(10)
Total other comprehensive (loss)/income, net of tax		1,318	(2,528)	21,292	(16,793)
Balance		3,527	(26,612)	3,527	(26,612)
Reclassification adjustment for stranded tax effects of Tax Cuts and Job Act, net of tax	[1]			0	(200)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Net unrealized (losses)/gains arising during the period, pre-tax		(1,126)	2,365	(5,848)	6,523
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		0	0	0	0
Total other comprehensive (loss)/income, pre-tax		(1,126)	2,365	(5,848)	6,523
Net unrealized (losses)/gains arising during the period, tax		(333)	699	(1,729)	1,928
Reclassification adjustment for net losses/(gains) included in net income, tax		0	0	0	0
Total other comprehensive (loss)/income, tax		(333)	699	(1,729)	1,928
Reclassification adjustment for stranded tax effects of Tax Cuts and Job Act, tax	[1]			0	315
Balance		(3,567)	1,163	(241)	(1,451)
Net unrealized (losses)/gains arising during the period, net of tax		(793)	1,666	(4,119)	4,595
Reclassification adjustment for net losses/(gains) included in net income, net of tax		0	0	0	0
Total other comprehensive (loss)/income, net of tax		(793)	1,666	(4,119)	4,595
Balance		(4,360)	2,829	(4,360)	2,829
Reclassification adjustment for stranded tax effects of Tax Cuts and Job Act, net of tax	[1]			0	(315)
AOCI Attributable to Parent [Member]
Net unrealized (losses)/gains arising during the period, pre-tax		624	(1,238)	24,271	(17,331)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax		(121)	(14)	(108)	(14)
Total other comprehensive (loss)/income, pre-tax		745	(1,224)	24,379	(17,317)
Reclassification adjustment for equity securities, pre-tax	[2]			0	(12,151)
Net unrealized (losses)/gains arising during the period, tax		184	(366)	7,174	(5,123)
Reclassification adjustment for net losses/(gains) included in net income, tax		(36)	(4)	(32)	(4)
Total other comprehensive (loss)/income, tax		220	(362)	7,206	(5,119)
Reclassification adjustment for stranded tax effects of Tax Cuts and Job Act, tax	[1]			0	515
Reclassification adjustment for equity securities, tax	[2]			0	(3,592)
Balance		(1,358)	(22,921)	(18,006)	(2,511)
Net unrealized (losses)/gains arising during the period, net of tax		440	(872)	17,097	(12,208)
Reclassification adjustment for net losses/(gains) included in net income, net of tax		(85)	(10)	(76)	(10)
Total other comprehensive (loss)/income, net of tax		525	(862)	17,173	(12,198)
Balance		$ (833)	$ (23,783)	(833)	(23,783)
Reclassification adjustment for stranded tax effects of Tax Cuts and Job Act, net of tax	[1]			0	(515)
Reclassification adjustment for equity securities, net of tax	[2]			$ 0	$ (8,559)

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

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