Shareholders' Equity (Details Narrative) - USD ($)										3 Months Ended												12 Months Ended			14 Months Ended
	Aug. 31, 2017	Aug. 02, 2017	Jul. 26, 2017	Jun. 05, 2017	Jun. 02, 2017	Aug. 11, 2016	Apr. 05, 2016	Apr. 04, 2016	Oct. 20, 2015	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2016
Discount rate on purchase price under dividend reinvestment plan																						95.00%
Proceeds from issuance of offering																						$ 22,518,238	$ 0	$ 0
Preferred stock redemption charge										$ 0				$ 91,595,000								$ 0	$ 91,595,000		$ 91,595,000
Dividend declared per share, paid										$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.18	$ 0.72	$ 0.72	$ 0.72
Dividend paid date																						Feb. 15, 2018
Record date of dividend																						Mar. 15, 2018
Net proceeds from issuance of shares																						$ 138,975,847	$ 49,120,853	$ 43,042,124
Common stock shares authorized										113,663,800				75,000,000								113,663,800	75,000,000		75,000,000
Excess stock, shares authorized										3,000,000				3,000,000								3,000,000	3,000,000		3,000,000
Shares authorized								81,663,800
January 25, 2018 [Member]
Number of share authorized to repurchase under Share Repurchase Program										10,000,000												10,000,000
Maryland State Department of Assessments and Taxation [Member]
Increase in authorized number of shares									22,000,000
Common stock shares authorized									48,663,800
Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Increase in authorized number of shares					10,000,000
Excess stock, shares authorized						3,000,000		3,000,000
8.25% Series A Cumulative Redeemable Preferred Stock [Member]
Cumulative redeemable preferred stock, authorized	3,663,800
Cumulative redeemable preferred stock percentage	8.25%
Preferred Stock, Liquidation Preference Per Share	$ 25.00
Preferred stock, redemption price per share	$ 25.00
Preferred stock redemption charge	$ 91,595,000
Dividends paid	$ 1,889,147
Dividend declared per share, paid	$ 0.515625
Dividend paid date	Sep. 15, 2017
Record date of dividend	Aug. 15, 2017
8.25% Series A Cumulative Redeemable Preferred Stock [Member] | Board of Directors [Member]
Dividends paid	$ 3,502,000
Series B Cumulative Redeemable Preferred Stock [Member]
Dividends paid																									$ 710,610
Dividend paid date																									Mar. 15, 2016
Cumulative redeemable preferred stock, shares issued									1,801,200	3,801,200				3,801,200								3,801,200	3,801,200		3,801,200
Percentage rate on cumulative redeemable preferred stock									8.00%	8.00%				8.00%								8.00%	8.00%		8.00%
Cumulative redemption price per share									$ 25.00
Net proceeds from issuance of shares									$ 43,000,000
Description of preferred stock dividend									Annual rate of $2.00 per share and will be payable quarterly in arrears at March 15, June 15, September 15, and December 15.
Preferred stock par value										$ 0.10				$ 0.10								$ 0.10	$ 0.10		$ 0.10
Shares issued price per share										$ 25.00												$ 25.00
Preferred stock, shares outstanding										3,801,200				3,801,200								3,801,200	3,801,200		3,801,200
Series B Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Cumulative redeemable preferred stock, authorized								2,000,000
Excess stock, shares authorized								3,000,000
Series B Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Cumulative redeemable preferred stock, authorized						4,000,000		4,000,000
Series A Cumulative Redeemable Preferred Stock [Member]
Cumulative redeemable preferred stock, authorized			3,663,800
Cumulative redeemable preferred stock, shares issued										0				3,663,800								0	3,663,800		3,663,800
Percentage rate on cumulative redeemable preferred stock										8.25%				8.25%								8.25%	8.25%		8.25%
Preferred stock par value			$ 0.10							$ 0.10				$ 0.10								$ 0.10	$ 0.10		$ 0.10
Increase in authorized number of shares	113,663,800
Preferred stock, shares outstanding	3,663,800									0				3,663,800								0	3,663,800		3,663,800
Series A Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Cumulative redeemable preferred stock, authorized								3,663,800
Excess stock, shares authorized									3,000,000
Series A Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Cumulative redeemable preferred stock, authorized						3,663,800		3,663,800
Series B Preferred Stock [Member]
Number of stock sold during period							2,000,000
Sale of stock price per share							$ 25.50
Proceeds from sale of common stock							$ 49,100,000
Series B Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Common stock shares authorized								2,000,000
Common Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Common stock shares authorized						71,000,000
Excess stock, shares authorized			85,000,000
Shares authorized						85,663,800
Common Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Common stock shares authorized						75,000,000
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
Preferred Stock, Liquidation Preference Per Share			$ 25.00
Preferred stock, redemption price per share			$ 25.00
Dividends paid			$ 970,312
Dividend declared per share, paid			$ 0.16875
Dividend paid date			Sep. 15, 2017
Record date of dividend			Aug. 31, 2017
Cumulative redeemable preferred stock, shares issued			5,000,000
Net proceeds from issuance of shares		$ 18,200,000
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.
Exercised overallotment option and purchased additional shares		750,000
Annual rate on dividend per share payable quarterly			$ 1.6875
Series C Preferred Stock [Member]
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 A Preferred Shares [Member]
Cumulative redeemable preferred stock, authorized			3,663,800
Series B Preferred Shares [Member]
Cumulative redeemable preferred stock, authorized			4,000,000
Excess stock, shares authorized			3,000,000
Series C Preferred Shares [Member]
Cumulative redeemable preferred stock, authorized			5,750,000
Excess stock, shares authorized			3,000,000
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] | Amendment [Member]
Common stock shares authorized								71,000,000
Common Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Common stock shares authorized									62,000,000
Common Stock [Member] | Series B Cumulative Redeemable Preferred Stock [Member]
Common stock shares authorized									2,000,000
8% Series B Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Cumulative redeemable preferred stock, authorized									2,000,000
Minimum [Member]
Amount of optional cash payments																						$ 500
Minimum [Member] | Common Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Common stock shares authorized								62,000,000	42,000,000
Minimum [Member] | 8.25% Series A Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Cumulative redeemable preferred stock, authorized									3,663,800
Maximum [Member]
Amount of optional cash payments																						$ 1,000
Increase in authorized number of shares								11,000,000
Shares authorized								70,663,800
Maximum [Member] | Maryland State Department of Assessments and Taxation [Member]
Increase in authorized number of shares									70,663,800
Maximum [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Excess stock, shares authorized						3,000,000
Maximum [Member] | Series B Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Cumulative redeemable preferred stock, authorized						4,000,000
Maximum [Member] | Series A Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Cumulative redeemable preferred stock, authorized						3,663,800
Maximum [Member] | Series C Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Increase in authorized number of shares			126,413,800
Maximum [Member] | Series A Preferred Shares [Member]
Common stock shares authorized			115,750,000
Maximum [Member] | Common Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Increase in authorized number of shares						4,000,000
Common stock shares authorized								73,000,000	64,000,000
Shares authorized						81,663,800
Maximum [Member] | Common Stock [Member] | Maryland State Department of Assessments and Taxation [Member] | Amendment [Member]
Common stock shares authorized						81,663,800
Maximum [Member] | 8.25% Series A Cumulative Redeemable Preferred Stock [Member] | Maryland State Department of Assessments and Taxation [Member]
Cumulative redeemable preferred stock, authorized									3,663,800