Income Taxes Distributions Paid (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Common Shares [Member]
Class of Stock [Line Items]
Ordinary Non-Qualified Income Per Share	$ 1.3611	$ 1.3794	$ 1.1715
Percentage of Ordinary Non-Qualified Income	95.41%	95.14%	98.21%
Qualified Dividend per Share	$ 0.0256	$ 0.0704	$ 0.0213
Percentage of Qualified Dividend	1.79%	4.86%	1.79%
Capital Gain Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Capital Gain	0.00%	0.00%	0.00%
Return of Capital Per Share	$ 0.0399	$ 0.0000	$ 0.0000
Percentage of Return of Capital	2.80%	0.00%	0.00%
Distributions Paid Per Share on a Tax Basis	$ 1.4266	$ 1.4498	$ 1.1928
Percentage of Distributions Paid Per Share on a Tax Basis	100.00%	100.00%	100.00%
7.875% Series A [Member]
Class of Stock [Line Items]
Ordinary Non-Qualified Income Per Share	$ 0.0000	$ 0.2914	$ 1.9336
Percentage of Ordinary Non-Qualified Income	0.00%	95.14%	98.21%
Qualified Dividend per Share	$ 0.0000	$ 0.0149	$ 0.0352
Percentage of Qualified Dividend	0.00%	4.86%	1.79%
Capital Gain Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Capital Gain	0.00%	0.00%	0.00%
Return of Capital Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Return of Capital	0.00%	0.00%	0.00%
Distributions Paid Per Share on a Tax Basis	$ 0.0000	$ 0.3063	$ 1.9688
Percentage of Distributions Paid Per Share on a Tax Basis	0.00%	100.00%	100.00%
8.00% Series B [Member]
Class of Stock [Line Items]
Ordinary Non-Qualified Income Per Share	$ 0.0000	$ 1.3109	$ 1.9643
Percentage of Ordinary Non-Qualified Income	0.00%	95.14%	98.21%
Qualified Dividend per Share	$ 0.0000	$ 0.0669	$ 0.0357
Percentage of Qualified Dividend	0.00%	4.86%	1.79%
Capital Gain Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Capital Gain	0.00%	0.00%	0.00%
Return of Capital Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Return of Capital	0.00%	0.00%	0.00%
Distributions Paid Per Share on a Tax Basis	$ 0.0000	$ 1.3778	$ 2.0000
Percentage of Distributions Paid Per Share on a Tax Basis	0.00%	100.00%	100.00%
6.50% Series C [Member]
Class of Stock [Line Items]
Ordinary Non-Qualified Income Per Share	$ 1.1969	$ 1.5461	$ 1.5960
Percentage of Ordinary Non-Qualified Income	98.20%	95.14%	98.22%
Qualified Dividend per Share	$ 0.0219	$ 0.0789	$ 0.0290
Percentage of Qualified Dividend	1.80%	4.86%	1.78%
Capital Gain Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Capital Gain	0.00%	0.00%	0.00%
Return of Capital Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Return of Capital	0.00%	0.00%	0.00%
Distributions Paid Per Share on a Tax Basis	$ 1.2188	$ 1.6250	$ 1.6250
Percentage of Distributions Paid Per Share on a Tax Basis	100.00%	100.00%	100.00%
6.375% Series D [Member]
Class of Stock [Line Items]
Ordinary Non-Qualified Income Per Share	$ 1.1739	$ 0.9099	$ 0.0000
Percentage of Ordinary Non-Qualified Income	98.21%	95.15%	0.00%
Qualified Dividend per Share	$ 0.0214	$ 0.0464	$ 0.0000
Percentage of Qualified Dividend	1.79%	4.85%	0.00%
Capital Gain Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Capital Gain	0.00%	0.00%	0.00%
Return of Capital Per Share	$ 0.0000	$ 0.0000	$ 0.0000
Percentage of Return of Capital	0.00%	0.00%	0.00%
Distributions Paid Per Share on a Tax Basis	$ 1.1953	$ 0.9563	$ 0.0000
Percentage of Distributions Paid Per Share on a Tax Basis	100.00%	100.00%	0.00%