Note 12 - Stockholders' Equity and Earnings Per Share - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Beginning balance, loss, net of tax	$ 1,747,778	$ 1,602,888	$ 1,458,971
Total other comprehensive (loss)/income, net of tax	4,711	(2,857)	24,160
Ending balance, loss, net of tax	1,828,539	1,747,778	1,602,888
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Beginning balance, loss, net of tax	(5,431)	(3,172)
Net unrealized (losses)/gains arising during the period, pre-tax	11,603	(7,247)
Net unrealized (losses)/gains arising during the period, tax	4,878	(3,047)
Net unrealized (losses)/gains arising during the period, net of tax	6,725	(4,200)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax	(4,898)	3,349
Reclassification adjustment for net losses/(gains) included in net income, tax	(2,059)	1,408
Reclassification adjustment for net losses/(gains) included in net income, net of tax	(2,839)	1,941
Total other comprehensive (loss)/income, pre-tax	6,705	(3,898)
Total other comprehensive (loss)/income, tax	2,819	(1,639)
Total other comprehensive (loss)/income, net of tax	3,886	(2,259)
Ending balance, loss, net of tax	(1,545)	(5,431)	(3,172)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Beginning balance, loss, net of tax	(2,995)	(2,397)
Net unrealized (losses)/gains arising during the period, pre-tax	1,423	(1,032)
Net unrealized (losses)/gains arising during the period, tax	598	(434)
Net unrealized (losses)/gains arising during the period, net of tax	825	(598)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax
Reclassification adjustment for net losses/(gains) included in net income, tax
Reclassification adjustment for net losses/(gains) included in net income, net of tax
Total other comprehensive (loss)/income, pre-tax	1,423	(1,032)
Total other comprehensive (loss)/income, tax	598	(434)
Total other comprehensive (loss)/income, net of tax	825	(598)
Ending balance, loss, net of tax	(2,170)	(2,995)	(2,397)
AOCI Attributable to Parent [Member]
Beginning balance, loss, net of tax	(8,426)	(5,569)	(29,729)
Net unrealized (losses)/gains arising during the period, pre-tax	13,026	(8,279)
Net unrealized (losses)/gains arising during the period, tax	5,476	(3,481)
Net unrealized (losses)/gains arising during the period, net of tax	7,550	(4,798)
Reclassification adjustment for net losses/(gains) included in net income, pre-tax	(4,898)	3,349
Reclassification adjustment for net losses/(gains) included in net income, tax	(2,059)	1,408
Reclassification adjustment for net losses/(gains) included in net income, net of tax	(2,839)	1,941
Total other comprehensive (loss)/income, pre-tax	8,128	(4,930)
Total other comprehensive (loss)/income, tax	3,417	(2,073)
Total other comprehensive (loss)/income, net of tax	4,711	(2,857)	24,160
Ending balance, loss, net of tax	$ (3,715)	$ (8,426)	$ (5,569)