Income Taxes - Federal Income Tax Treatment of Common Dividends (Details) - Common Stock - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax [Line Items]
Ordinary Income (A)	$ 0.6858	$ 0.6552	$ 0.6935
Unrecaptured Section 1250 Gain	0.1497	0.1627	0.1130
Capital Gain	0.0330	0.0648	0.0066
Qualified Dividend	0.0015	0.0000	0.0000
Return of Capital	0.0000	0.0000	0.0272
Distributions Per Common Share	$ 0.8700	$ 0.8827	$ 0.8403
Ordinary Income as a Percentage of Distributions	78.83%	74.23%	82.53%
Unrecaptured Section 1250 Gain as a Percentage of Distributions	17.21%	18.43%	13.45%
Capital Gain as a Percentage of Distributions	3.79%	7.34%	0.78%
Qualified Dividend as a Percentage Of Distributions	0.17%	0.00%	0.00%
Return of Capital as a Percentage of Distributions	0.00%	0.00%	3.24%
Common Distributions Percentage	100.00%	100.00%	100.00%