Summary of Significant Accounting Policies Tax (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary Of Significant Accounting Policies [Abstract]
State and local income, franchise and excise tax (benefit)	$ 963	$ 878	$ 478
Alternative minimum tax credit (benefit)	(3,244)
Income and other tax expense (benefit)	$ (2,281)	$ 878	$ 478
Tax Treatment Of Dividends And Distributions Ordinary Dividends	$ 1.39604	$ 1.84454	$ 1.22126
Tax Treatment Of Dividends And Distributions Long Term Capital Gain	0.61243	0.21423	0.18959
Tax Treatment Of Dividends And Distributions Unrecaptured Section Twelve Hundred And Fifty Gain	0.23403	0.06498	0.10040
Dividends and distributions declared per Common Share outstanding	$ 2.24250	$ 2.12375	$ 1.51125