Note 21 - Income Taxes (Details) - Taxable Characteristics of Distributions Paid - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Preferred H Dividends
Dividends distributed, amount	$ 454,036	$ 426,344	$ 399,030
Series H Preferred Stock [Member]
Preferred H Dividends
Ordinary income, amount		$ 6,762	$ 8,694
Ordinary income, percent		56.00%	72.00%
Capital gain, amount	$ 13,417	$ 5,313	$ 3,381
Capital gain, percent	100.00%	44.00%	28.00%
Dividends distributed, amount	$ 13,417	$ 12,075	$ 12,075
Dividends distributed, percent	100.00%	100.00%	100.00%
Series I Preferred Stock [Member]
Preferred H Dividends
Ordinary income, amount		$ 13,440	$ 17,280
Ordinary income, percent		56.00%	72.00%
Capital gain, amount	$ 24,000	$ 10,560	$ 6,720
Capital gain, percent	100.00%	44.00%	28.00%
Dividends distributed, amount	$ 24,000	$ 24,000	$ 24,000
Dividends distributed, percent	100.00%	100.00%	100.00%
Series J Preferred Stock [Member]
Preferred H Dividends
Ordinary income, amount		$ 6,930	$ 8,910
Ordinary income, percent		56.00%	72.00%
Capital gain, amount	$ 12,375	$ 5,445	$ 3,465
Capital gain, percent	100.00%	44.00%	28.00%
Dividends distributed, amount	$ 12,375	$ 12,375	$ 12,375
Dividends distributed, percent	100.00%	100.00%	100.00%
Series K Preferred Stock [Member]
Preferred H Dividends
Ordinary income, amount		$ 5,513	$ 6,064
Ordinary income, percent		56.00%	72.00%
Capital gain, amount	$ 9,844	$ 4,331	$ 2,358
Capital gain, percent	100.00%	44.00%	28.00%
Dividends distributed, amount	$ 9,844	$ 9,844	$ 8,422
Dividends distributed, percent	100.00%	100.00%	100.00%
Common Stock [Member]
Preferred H Dividends
Ordinary income, amount		$ 132,498	$ 157,393
Ordinary income, percent		36.00%	46.00%
Capital gain, amount	$ 394,400	$ 103,054	$ 61,588
Capital gain, percent	100.00%	28.00%	18.00%
Return of capital		$ 132,498	$ 123,177
Return of capital		36.00%	36.00%
Dividends distributed, amount	$ 394,400	$ 368,050	$ 342,158
Dividends distributed, percent	100.00%	100.00%	100.00%