Distributions - Summary of Payment of Dividends to Preferred Shareholders (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Declaration Date	Jan. 15, 2019
Record Date	Mar. 15, 2019
Payment Date	Feb. 15, 2019
Preferred stock, dividend declared per share, paid	$ 0.55	$ 0.52	$ 0.51
Series A Preferred Stock [Member]
Amount of distributions paid for preferred stock		$ 5,667,441	$ 7,556,588
Preferred stock, dividend declared per share, paid		$ 1.546875	$ 2.0625
Series A Preferred Stock [Member] | Dividend Payment Date One [Member]
Declaration Date		Jan. 19, 2017
Record Date		Feb. 15, 2017
Payment Date		Mar. 15, 2017
Amount of distributions paid for preferred stock		$ 1,889,147
Preferred stock, dividend declared per share, paid		$ 0.515625
Series A Preferred Stock [Member] | Dividend Payment Date Two [Member]
Declaration Date		Apr. 03, 2017
Record Date		May 15, 2017
Payment Date		Jun. 15, 2017
Amount of distributions paid for preferred stock		$ 1,889,147
Preferred stock, dividend declared per share, paid		$ 0.515625
Series A Preferred Stock [Member] | Dividend Payment Date Three [Member]
Declaration Date		Jul. 03, 2017
Record Date		Aug. 15, 2017
Payment Date		Sep. 15, 2017
Amount of distributions paid for preferred stock		$ 1,889,147
Preferred stock, dividend declared per share, paid		$ 0.515625
Series A Preferred Stock [Member] | Dividend Payment Date Four [Member]
Declaration Date			Jan. 15, 2016
Record Date			Feb. 16, 2016
Payment Date			Mar. 15, 2016
Amount of distributions paid for preferred stock			$ 1,889,147
Preferred stock, dividend declared per share, paid			$ 0.515625
Series A Preferred Stock [Member] | Dividend Payment Date Five [Member]
Declaration Date			Apr. 04, 2016
Record Date			May 16, 2016
Payment Date			Jun. 15, 2016
Amount of distributions paid for preferred stock			$ 1,889,147
Preferred stock, dividend declared per share, paid			$ 0.515625
Series A Preferred Stock [Member] | Dividend Payment Date Six [Member]
Declaration Date			Jul. 01, 2016
Record Date			Aug. 15, 2016
Payment Date			Sep. 15, 2016
Amount of distributions paid for preferred stock			$ 1,889,147
Preferred stock, dividend declared per share, paid			$ 0.515625
Series A Preferred Stock [Member] | Dividend Payment Date Seven [Member]
Declaration Date			Oct. 03, 2016
Record Date			Nov. 17, 2016
Payment Date			Dec. 15, 2016
Amount of distributions paid for preferred stock			$ 1,889,147
Preferred stock, dividend declared per share, paid			$ 0.515625
Series B Preferred Stock [Member]
Amount of distributions paid for preferred stock	$ 7,602,400	$ 7,602,400	$ 7,007,057
Preferred stock, dividend declared per share, paid	$ 2.00	$ 2.00	$ 2.22466
Series B Preferred Stock [Member] | Dividend Payment Date One [Member]
Declaration Date	Jan. 15, 2018
Record Date	Feb. 15, 2018
Payment Date	Mar. 15, 2018
Amount of distributions paid for preferred stock	$ 1,900,600
Preferred stock, dividend declared per share, paid	$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Two [Member]
Declaration Date	Apr. 01, 2018
Record Date	May 15, 2018
Payment Date	Jun. 15, 2018
Amount of distributions paid for preferred stock	$ 1,900,600
Preferred stock, dividend declared per share, paid	$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Three [Member]
Declaration Date	Jul. 01, 2018
Record Date	Aug. 15, 2018
Payment Date	Sep. 17, 2018
Amount of distributions paid for preferred stock	$ 1,900,600
Preferred stock, dividend declared per share, paid	$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Four [Member]
Declaration Date	Oct. 01, 2018
Record Date	Nov. 15, 2018
Payment Date	Dec. 17, 2018
Amount of distributions paid for preferred stock	$ 1,900,600
Preferred stock, dividend declared per share, paid	$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Five [Member]
Declaration Date		Jan. 19, 2017
Record Date		Feb. 15, 2017
Payment Date		Mar. 15, 2017
Amount of distributions paid for preferred stock		$ 1,900,600
Preferred stock, dividend declared per share, paid		$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Six [Member]
Declaration Date		Apr. 03, 2017
Record Date		May 15, 2017
Payment Date		Jun. 15, 2017
Amount of distributions paid for preferred stock		$ 1,900,600
Preferred stock, dividend declared per share, paid		$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Seven [Member]
Declaration Date		Jul. 03, 2017
Record Date		Aug. 15, 2017
Payment Date		Sep. 15, 2017
Amount of distributions paid for preferred stock		$ 1,900,600
Preferred stock, dividend declared per share, paid		$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Eight [Member]
Declaration Date		Oct. 02, 2017
Record Date		Nov. 15, 2017
Payment Date		Dec. 15, 2017
Amount of distributions paid for preferred stock		$ 1,900,600
Preferred stock, dividend declared per share, paid		$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Nine [Member]
Declaration Date			Jan. 15, 2016
Record Date			Feb. 16, 2016
Payment Date			Mar. 15, 2016
Amount of distributions paid for preferred stock			$ 1,305,257
Preferred stock, dividend declared per share, paid			$ 0.72466
Series B Preferred Stock [Member] | Dividend Payment Date Ten [Member]
Declaration Date			Apr. 04, 2016
Record Date			May 16, 2016
Payment Date			Jun. 15, 2016
Amount of distributions paid for preferred stock			$ 1,900,600
Preferred stock, dividend declared per share, paid			$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Eleven [Member]
Declaration Date			Jul. 01, 2016
Record Date			Aug. 15, 2016
Payment Date			Sep. 15, 2016
Amount of distributions paid for preferred stock			$ 1,900,600
Preferred stock, dividend declared per share, paid			$ 0.50
Series B Preferred Stock [Member] | Dividend Payment Date Twelve [Member]
Declaration Date			Oct. 03, 2016
Record Date			Nov. 17, 2016
Payment Date			Dec. 15, 2016
Amount of distributions paid for preferred stock			$ 1,900,600
Preferred stock, dividend declared per share, paid			$ 0.50
Series C Preferred Stock [Member]
Amount of distributions paid for preferred stock	$ 9,703,124	$ 3,396,094
Preferred stock, dividend declared per share, paid	$ 1.68750	$ 0.590625
Series C Preferred Stock [Member] | Dividend Payment Date One [Member]
Declaration Date	Jan. 15, 2018
Record Date	Feb. 15, 2018
Payment Date	Mar. 15, 2018
Amount of distributions paid for preferred stock	$ 2,425,781
Preferred stock, dividend declared per share, paid	$ 0.421875
Series C Preferred Stock [Member] | Dividend Payment Date Two [Member]
Declaration Date	Apr. 01, 2018
Record Date	May 15, 2018
Payment Date	Jun. 15, 2018
Amount of distributions paid for preferred stock	$ 2,425,781
Preferred stock, dividend declared per share, paid	$ 0.421875
Series C Preferred Stock [Member] | Dividend Payment Date Three [Member]
Declaration Date	Jul. 01, 2018
Record Date	Aug. 15, 2018
Payment Date	Sep. 17, 2018
Amount of distributions paid for preferred stock	$ 2,425,781
Preferred stock, dividend declared per share, paid	$ 0.421875
Series C Preferred Stock [Member] | Dividend Payment Date Four [Member]
Declaration Date	Oct. 01, 2018
Record Date	Nov. 15, 2018
Payment Date	Dec. 17, 2018
Amount of distributions paid for preferred stock	$ 2,425,781
Preferred stock, dividend declared per share, paid	$ 0.421875
Series C Preferred Stock [Member] | Dividend Payment Date Five [Member]
Declaration Date		Jul. 03, 2017
Record Date		Aug. 15, 2017
Payment Date		Sep. 15, 2017
Amount of distributions paid for preferred stock		$ 970,313
Preferred stock, dividend declared per share, paid		$ 0.168750
Series C Preferred Stock [Member] | Dividend Payment Date Six [Member]
Declaration Date		Oct. 02, 2017
Record Date		Nov. 15, 2017
Payment Date		Dec. 15, 2017
Amount of distributions paid for preferred stock		$ 2,425,781
Preferred stock, dividend declared per share, paid		$ 0.421875
Series D Preferred Stock [Member]
Amount of distributions paid for preferred stock	$ 2,744,794
Preferred stock, dividend declared per share, paid	$ 1.372397
Series D Preferred Stock [Member] | Dividend Payment Date One [Member]
Declaration Date	Jan. 15, 2018
Record Date	Feb. 15, 2018
Payment Date	Mar. 15, 2018
Amount of distributions paid for preferred stock	$ 354,166
Preferred stock, dividend declared per share, paid	$ 0.1770830
Series D Preferred Stock [Member] | Dividend Payment Date Two [Member]
Declaration Date	Apr. 01, 2018
Record Date	May 15, 2018
Payment Date	Jun. 15, 2018
Amount of distributions paid for preferred stock	$ 796,876
Preferred stock, dividend declared per share, paid	$ 0.3984375
Series D Preferred Stock [Member] | Dividend Payment Date Three [Member]
Declaration Date	Jul. 01, 2018
Record Date	Aug. 15, 2018
Payment Date	Sep. 17, 2018
Amount of distributions paid for preferred stock	$ 796,876
Preferred stock, dividend declared per share, paid	$ 0.3984375
Series D Preferred Stock [Member] | Dividend Payment Date Four [Member]
Declaration Date	Oct. 01, 2018
Record Date	Nov. 15, 2018
Payment Date	Dec. 17, 2018
Amount of distributions paid for preferred stock	$ 796,876
Preferred stock, dividend declared per share, paid	$ 0.3984375