Income Taxes (Distributions Paid) (Tables)

12 Months Ended

Dec. 31, 2017

Income Tax Disclosure [Abstract]

Schedule of Distributions Paid Per Common Share of Beneficial Interest and Preferred Shares on a Tax Basis

The following characterizes distributions paid per common share and preferred share on a tax basis for the years endedDecember 31, 2017, 2016 and 2015:

	2017				2016				2015
	Amount		%		Amount		%		Amount		%
Common Shares:
Ordinary non-qualified income	$	1.3611	95.41	%	$	1.3794	95.14	%	$	1.1715	98.21	%
Qualified dividend	0.0256		1.79	%	0.0704		4.86	%	0.0213		1.79	%
Capital gain	—		—	%	—		—	%	—		—	%
Return of capital	0.0399		2.80	%	—		—	%	—		—	%
Total	$	1.4266	100.00	%	$	1.4498	100.00	%	$	1.1928	100.00	%
Series A Preferred Shares:
Ordinary non-qualified income	$	—	—	%	$	0.2914	95.14	%	$	1.9336	98.21	%
Qualified dividend	—		—	%	0.0149		4.86	%	0.0352		1.79	%
Capital gain	—		—	%	—		—	%	—		—	%
Return of capital	—		—	%	—		—	%	—		—	%
Total	$	—	—	%	$	0.3063	100.00	%	$	1.9688	100.00	%
Series B Preferred Shares:
Ordinary non-qualified income	$	—	—	%	$	1.3109	95.14	%	$	1.9643	98.21	%
Qualified dividend	—		—	%	0.0669		4.86	%	0.0357		1.79	%
Capital gain	—		—	%	—		—	%	—		—	%
Return of capital	—		—	%	—		—	%	—		—	%
Total	$	—	—	%	$	1.3778	100.00	%	$	2.0000	100.00	%
Series C Preferred Shares:
Ordinary non-qualified income	$	1.1969	98.20	%	$	1.5461	95.14	%	$	1.5960	98.22	%
Qualified dividend	0.0219		1.80	%	0.0789		4.86	%	0.0290		1.78	%
Capital gain	—		—	%	—		—	%	—		—	%
Return of capital	—		—	%	—		—	%	—		—	%
Total	$	1.2188	100.00	%	$	1.6250	100.00	%	$	1.6250	100.00	%
Series D Preferred Shares:
Ordinary non-qualified income	$	1.1739	98.21	%	$	0.9099	95.15	%	$	—	—	%
Qualified dividend	0.0214		1.79	%	0.0464		4.85	%	—		—	%
Capital gain	—		—	%	—		—	%	—		—	%
Return of capital	—		—	%	—		—	%	—		—	%
Total	$	1.1953	100.00	%	$	0.9563	100.00	%	$	—	—	%