Summary of Significant Accounting Policies Tax Characteristics of Dividends (Details)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	100.00%	100.00%	100.00%
Preferred Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid			100.00%
Ordinary Income [Member] | Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	72.60%	4.20%	59.20%
Ordinary Income [Member] | Preferred Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid			60.70%
Return of Capital [Member] | Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	2.60%	0.00%	2.50%
Capital Gains [Member] | Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	24.80%	95.80%	38.30%
Capital Gains [Member] | Preferred Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid			39.30%