Summary of Significant Accounting Policies Tax Characteristics of Dividends (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Tax Characterization of Dividends Paid [Line Items]
Income Taxes Paid, Net	$ 3,700,000	$ 21,000,000	$ 600,000
Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	100.00%	100.00%	100.00%
Ordinary Income [Member] | Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	78.40%	23.70%	72.60%
Return of Capital [Member] | Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid			2.60%
Capital Gains [Member] | Common Stock [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	21.60%	76.30%	24.80%