Real Estate - Schedule of Property Dispositions (Details) - USD ($)	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	Dec. 31, 2017	Dec. 31, 2016
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income									$ 124,498,400	$ 188,019,112	$ 192,088,348
Tenant reimbursements and other									17,490,459	24,950,128	26,149,184
Total revenues	$ 36,235,206	$ 36,241,718	$ 34,057,008	$ 35,454,927	$ 47,978,462	$ 55,592,107	$ 55,118,406	$ 54,280,265	141,988,859	212,969,240	218,237,532
Operating, maintenance and management									38,512,239	58,347,903	57,832,187
Real estate taxes and insurance									24,230,326	35,114,937	36,507,827
Fees to affiliates									15,879,702	21,960,145	25,440,718
Depreciation and amortization									46,109,794	67,755,152	69,513,484
Interest expense									33,158,759	44,114,130	41,772,682
Loss on debt extinguishment									3,621,665	2,380,051	4,932,369
General and administrative expenses									6,269,238	6,732,330	7,817,916
Total expenses									167,781,723	236,404,648	243,817,183
Discontinued Operations, Disposed of by Sale [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income									15,419,070	86,308,663	90,745,815
Tenant reimbursements and other									2,387,947	12,181,764	12,559,674
Total revenues									17,807,017	98,490,427	103,305,489
Operating, maintenance and management									6,071,075	28,762,439	28,943,711
Real estate taxes and insurance									3,085,761	17,266,260	18,011,156
Fees to affiliates									755,971	3,832,896	3,950,983
Depreciation and amortization									4,391,426	30,106,602	32,827,001
Interest expense									3,731,580	19,344,126	18,120,461
Loss on debt extinguishment									3,346,271	2,387,552	1,569,888
General and administrative expenses									584,621	1,217,005	1,168,334
Total expenses									$ 21,966,705	$ 102,916,880	$ 104,591,534