Income Taxes (Summary Of Distributions Paid) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Class of Stock [Line Items]
Common Shares, Ordinary income, Amount	$ 0.156000	$ 0.455000
Common Shares, Capital gain, Amount
Common Shares, Return of capital, Amount	0.624000
Common Shares, Total, Amount	$ 0.780000	$ 0.455000
Common Shares, Ordinary income, Percent	20.00%	100.00%
Common Shares, Capital gain, Percent
Common Shares, Return of capital, Percent	80.00%
Common Shares, Total, Percent	100.00%	100.00%
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Shares, Ordinary income, Amount		$ 1.649124
Preferred Shares, Capital gain, Amount
Preferred Shares, Return of capital, Amount
Preferred Shares, Total, Amount		$ 1.649124
Preferred Shares, Ordinary income, Percent		100.00%
Preferred Shares, Capital gain, Percent
Preferred Shares, Return of capital, Percent
Preferred Shares, Total, Percent		100.00%
Series D Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Shares, Ordinary income, Amount	$ 0.104160	$ 0.494792
Preferred Shares, Capital gain, Amount
Preferred Shares, Return of capital, Amount
Preferred Shares, Total, Amount	$ 0.104160	$ 0.494792
Preferred Shares, Ordinary income, Percent	100.00%	100.00%
Preferred Shares, Capital gain, Percent
Preferred Shares, Return of capital, Percent
Preferred Shares, Total, Percent	100.00%	100.00%
Series E Preferred Stock [Member]
Class of Stock [Line Items]
Preferred Shares, Ordinary income, Amount	$ 0.522569
Preferred Shares, Capital gain, Amount
Preferred Shares, Return of capital, Amount
Preferred Shares, Total, Amount	$ 0.522569
Preferred Shares, Ordinary income, Percent	100.00%
Preferred Shares, Capital gain, Percent
Preferred Shares, Return of capital, Percent
Preferred Shares, Total, Percent	100.00%