Shareholders' Equity (Details) - $ / shares	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018
Class of Stock [Line Items]
Preferred stock, shares authorized	50,000,000				50,000,000				50,000,000
Preferred stock, par value	$ 0.01				$ 0.01				$ 0.01
Preferred stock, shares issued	5,954,594				5,888,680				5,954,594
Preferred Stock, Liquidation Preference Per Share	$ 25.00								$ 25.00
Preferred Stock, Dividend Payment Terms									The Series A Preferred Stock pays a cumulative cash dividend equivalent to 8.50% of the $25.00 liquidation preference per share each year and the Series B Preferred Stock pays a cumulative cash dividend equivalent to 7.625% of the $25.00 liquidation preference per share each year.
Dividends declared per common share	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized	8,000,000								8,000,000
Preferred stock, shares issued	2,300,000				2,300,000				2,300,000
Preferred Stock, Dividend Rate, Percentage									8.50%
Series B Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares authorized	7,000,000								7,000,000
Preferred stock, shares issued	3,654,594				3,588,680				3,654,594
Preferred Stock, Dividend Rate, Percentage									7.625%
Preferred Stock
Class of Stock [Line Items]
Dividends Payable, Date to be Paid		Jan. 15, 2019
Dividends Payable, Date of Record		Jan. 01, 2019
Common Stock
Class of Stock [Line Items]
Dividends Payable, Date to be Paid		Jan. 31, 2019
Dividends Payable, Date of Record		Dec. 31, 2018