Distributions - Tax Characteristics of Distributions (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Distributions [Abstract]
Common Share Distributions Payments of Ordinary Dividends	$ 0	$ 0.36	$ 0.41
Common Share Distributions Capital Gain	0.62	0.14	0.02
Common Share Distributions Non-taxable Distributions	0	0.10	0.17
Common Stock, Dividends, Per Share, Paid	$ 0.62	$ 0.60	$ 0.60
Percentage Of Distributions classified as ordinary income	0.00%	59.10%	69.00%
Percentage Of Distributions classified as capital gain	100.00%	23.50%	3.30%
Percentage Of Distributions classified as non-taxable distribution	0.00%	17.40%	27.70%
Dividends, Preferred Stock	$ 6,900	$ 6,900	$ 6,900
Percentage Of Preferred Distributions classified as ordinary income	100.00%	100.00%	100.00%