Summary of Significant Accounting Policies Tax Characteristics of Dividends (Details) - Common Stock [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	100.00%	100.00%	100.00%
Ordinary Income [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	74.60%	80.70%	78.40%
Capital Gains [Member]
Tax Characterization of Dividends Paid [Line Items]
Percent of Total Dividends Paid	25.40%	19.30%	21.60%