Shareholders' Equity (Details Narrative) - USD ($)				6 Months Ended
	Jun. 15, 2017	Jun. 05, 2017	May 15, 2017	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Proceeds from issuance of offering				$ 22,527,507	$ 0
Proceed from dividend reinvestment and stock purchase plan (DRIP)				1,386,320	1,109,078
Preferred stock redemption amount				91,595,000		$ 91,595,000
Net proceeds from issuance of shares				$ 0	$ 49,120,853
Common stock shares authorized				85,000,000		75,000,000
Excess stock, shares authorized				3,000,000		3,000,000
DRIP [Member]
New shares issued under DRIP, value				$ 30,045,558
New shares issued under DRIP				2,062,546
Common Stock [Member]
Proceed from dividend reinvestment and stock purchase plan (DRIP)				$ 1,386,320
Common Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Excess stock, shares authorized				85,000,000
8.25% Series A Cumulative Redeemable Preferred Stock [Member]
Dividends paid	$ 1,889,147			$ 3,778,294
Dividend declared per share, paid	$ 0.515625
Annual rate on dividend per share payable quarterly	$ 2.0625
Record date of dividend	May 15, 2017
Cumulative redeemable preferred stock percentage	8.25%
Preferred Stock, Liquidation Preference Per Share	$ 25.00
Cumulative redeemable preferred stock, authorized				3,663,800
8.25% Series A Cumulative Redeemable Preferred Stock [Member] | Maximum [Member]
Common stock shares authorized				115,750,000
8.0% Series B Cumulative Redeemable Preferred Stock [Member]
Dividends paid	$ 1,900,600			$ 3,801,200
Dividend declared per share, paid	$ 0.50
Annual rate on dividend per share payable quarterly	$ 2.00
Record date of dividend	May 15, 2017
Cumulative redeemable preferred stock percentage	8.00%
Preferred Stock, Liquidation Preference Per Share	$ 25.00
Cumulative redeemable preferred stock, authorized				4,000,000
Excess stock, shares authorized				3,000,000
8.0% Series B Cumulative Redeemable Preferred Stock [Member] | Maximum [Member]
Cumulative redeemable preferred stock, authorized				4,000,000
Excess stock, shares authorized				3,000,000
6.75% Series C Cumulative Redeemable Preferred Stock [Member]
Cumulative redeemable preferred stock, authorized				5,750,000
Excess stock, shares authorized				3,000,000
Series A Cumulative Redeemable Preferred Stock[Member]
Cumulative redeemable preferred stock, authorized				3,663,800
Cumulative redeemable preferred stock, shares issued				3,663,800		3,663,800
Preferred stock, shares outstanding				3,663,800		3,663,800
Preferred stock par value				$ 0.10		$ 0.10
Series C Preferred Stock [Member]
Number of stock sold during period				5,000,000
Preferred stock, redemption price per share				$ 25.00
Preferred stock par value				$ 0.10
Common stock shares authorized				110,000,000
Series C Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Increase in authorized number of shares				30,750,000
Excess stock, shares authorized				95,663,800
Series C Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Maximum [Member]
Increase in authorized number of shares				126,413,800
8.0% Series B Cumulative Redeemable Preferred Stock One [Member]
Cumulative redeemable preferred stock, authorized				4,000,000
July 3, 2017 [Member] | 8.25% Series A Cumulative Redeemable Preferred Stock [Member]
Dividend declared per share, paid				$ 0.515625
Dividend paid date				Sep. 15, 2017
Record date of dividend				Aug. 15, 2017
July 3, 2017 [Member] | 8.0% Series B Cumulative Redeemable Preferred Stock [Member]
Dividend declared per share, paid				$ 0.50
Dividend paid date				Sep. 15, 2017
Record date of dividend				Aug. 15, 2017
July 31, 2017 [Member] | 8.25% Series A Cumulative Redeemable Preferred Stock [Member]
Cumulative redeemable preferred stock percentage				8.25%
Cumulative redeemable preferred stock, authorized				3,663,800
Preferred stock, redemption price per share				$ 25.00
Preferred stock redemption amount				$ 91,595,000
July 26, 2017 [Member] | 6.75% Series C Cumulative Redeemable Preferred Stock [Member]
Number of stock sold during period				5,000,000
Proceeds from issuance of offering				$ 120,800,000
Annual rate on dividend per share payable quarterly				$ 1.6875
Dividend paid date				Sep. 15, 2017
Record date of dividend				Aug. 31, 2017
Preferred stock, redemption price per share				$ 25.00
Cumulative redeemable preferred stock, shares issued				5,000,000
Description of preferred stock dividend				annual rate of $1.6875 per share and will be payable quarterly in arrears on March 15, June 15, September 15, and December 15.
August 2, 2017 [Member] | 6.75% Series C Cumulative Redeemable Preferred Stock [Member]
Exercised overallotment option and purchased additional shares				750,000
Net proceeds from issuance of shares				$ 18,200,000
Common Stock [Member]
Number of stock sold during period		1,400,000
Sale of stock price per share		$ 16.60
Proceeds from issuance of offering		$ 22,500,000
Common Stock [Member] | July 3, 2017 [Member]
Annual rate on dividend per share payable quarterly				$ 0.18
Dividend paid date				Sep. 15, 2017
Record date of dividend				Aug. 15, 2017
Common Stock [Member] | Common Shareholders [Member]
Dividends paid	$ 5,700,036			$ 11,116,863
Dividend declared per share, paid	$ 0.18
Proceed from dividend reinvestment and stock purchase plan (DRIP)			$ 704,817	$ 1,386,320