Note 19 - Stockholders' Equity - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019		Jun. 30, 2018
Beginning balance, loss, net of tax		$ 2,163,329	$ 2,009,792	$ 2,121,866		$ 1,973,304
Total other comprehensive (loss)/income, net of tax		9,073	(2,015)	16,648		(11,336)
Ending balance, loss, net of tax		2,199,297	2,064,833	2,199,297		2,064,833
AOCI, Accumulated Gain (Loss), Debt Securities, Available-for-sale, Parent [Member]
Beginning balance, loss, net of tax		(8,966)	(21,333)	(17,765)		(1,060)
Net unrealized (losses)/gains arising during the period, pre-tax		15,865	(3,905)	0	[1]	0	[1]
Net unrealized (losses)/gains arising during the period, tax		4,690	(1,154)	0	[1]	200	[1]
Net unrealized (losses)/gains arising during the period, net of tax		11,175	(2,751)	0	[1]	(200)	[1]
Total other comprehensive (loss)/income, pre-tax		15,865	(3,905)	28,356		(20,251)
Total other comprehensive (loss)/income, tax		4,690	(1,154)	8,382		(5,986)
Total other comprehensive (loss)/income, net of tax		11,175	(2,751)	19,974		(14,265)
Ending balance, loss, net of tax		2,209	(24,084)	2,209		(24,084)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax				28,356		(20,251)
Reclassification adjustment for net losses/(gains) included in net income, tax				8,382		(5,986)
Reclassification adjustment for net losses/(gains) included in net income, net of tax				19,974		(14,265)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Beginning balance, loss, net of tax		(1,465)	427	(241)		(1,451)
Net unrealized (losses)/gains arising during the period, pre-tax		(2,984)	1,045	0	[1]	0	[1]
Net unrealized (losses)/gains arising during the period, tax		(882)	309	0	[1]	315	[1]
Net unrealized (losses)/gains arising during the period, net of tax		(2,102)	736	0	[1]	(315)	[1]
Total other comprehensive (loss)/income, pre-tax		(2,984)	1,045	(4,722)		4,158
Total other comprehensive (loss)/income, tax		(882)	309	(1,396)		1,229
Total other comprehensive (loss)/income, net of tax		(2,102)	736	(3,326)		2,929
Ending balance, loss, net of tax		(3,567)	1,163	(3,567)		1,163
Reclassification adjustment for net losses/(gains) included in net income, pre-tax				(4,722)		4,158
Reclassification adjustment for net losses/(gains) included in net income, tax				(1,396)		1,229
Reclassification adjustment for net losses/(gains) included in net income, net of tax				(3,326)		2,929
AOCI Attributable to Parent [Member]
Beginning balance, loss, net of tax		(10,431)	(20,906)	(18,006)		(2,511)
Net unrealized (losses)/gains arising during the period, pre-tax		12,881	(2,860)	0	[1]	0	[1]
Net unrealized (losses)/gains arising during the period, tax		3,808	(845)	0	[1]	515	[1]
Net unrealized (losses)/gains arising during the period, net of tax		9,073	(2,015)	0	[1]	(515)	[1]
Total other comprehensive (loss)/income, pre-tax		12,881	(2,860)	23,634		(16,093)
Total other comprehensive (loss)/income, tax		3,808	(845)	6,986		(4,757)
Total other comprehensive (loss)/income, net of tax		9,073	(2,015)	16,648		(11,336)
Ending balance, loss, net of tax		$ (1,358)	$ (22,921)	(1,358)		(22,921)
Reclassification adjustment for equity securities, pre-tax	[2]			0		(12,151)
Reclassification adjustment for equity securities, tax	[2]			0		(3,592)
Reclassification adjustment for equity securities, net of tax	[2]			0		(8,559)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax				23,634		(16,093)
Reclassification adjustment for net losses/(gains) included in net income, tax				6,986		(4,757)
Reclassification adjustment for net losses/(gains) included in net income, net of tax				$ 16,648		$ (11,336)

[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.