Related Party Transactions - Additional Information (Detail)					1 Months Ended	12 Months Ended
	Dec. 23, 2016 shares	Dec. 20, 2016 USD ($)	Oct. 05, 2016 shares	May 07, 2013 Property	Jan. 31, 2017 USD ($)	Dec. 31, 2016 USD ($) Property $ / shares	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Related Party Transaction [Line Items]
Earned asset management fees						$ 1,420,000	$ 1,892,000	$ 4,191,000
Accrued interest receivable						36,271,000	47,343,000
Reimbursed compensation expense paid to IRT employees						$ 18,437,000	15,349,000	15,884,000
IRT
Related Party Transaction [Line Items]
Extended term of advisory agreement						Oct. 01, 2020
Management fee percentage				0.1875%		0.375%
Advisor incentive fee						20.00%
Internal return per share | $ / shares						$ 0.20
Number of properties excluded from computation of base management fee | Property				8
Earned asset management fees						$ 7,092,000	4,984,000	1,582,000
Incentive fees						350,000	629,000	154,000
Asset management fees and incentive fees receivables						0	1,854,000
Earned property and construction management fees						4,769,000	3,675,000	1,759,000
Property management and leasing fees						4,769,000	3,675,000	1,759,000
Property management and leasing fees receivables						$ 0	$ 440,000
Ownership percentage						0.00%	15.50%
Accrued interest receivable						$ 0
Received from IRT for shared service agreement						50,000
Payments for property management fees						23,000
Reimbursed compensation expense paid to IRT employees						253,000
IRT | Chief Executive Officer
Related Party Transaction [Line Items]
Compensation receive		$ 375,000
Number of shares awarded, share | shares	150,000
IRT | Chief Executive Officer | Six Month Anniversary
Related Party Transaction [Line Items]
Vesting percentage	50.00%
IRT | Chief Executive Officer | One Year Anniversary
Related Party Transaction [Line Items]
Vesting percentage	50.00%
IRT | Chief Executive Officer | Subsequent Event
Related Party Transaction [Line Items]
Cash payments					$ 500,000
IRT | Common Shares
Related Party Transaction [Line Items]
Number of shares sold to IRT | shares			7,269,719
IRT | Consolidation Eliminations
Related Party Transaction [Line Items]
Earned asset management fees						5,234,000	$ 4,984,000	1,582,000
Incentive fees						350,000	629,000	154,000
Property management and leasing fees						3,776,000	3,675,000	1,759,000
Dividends received						3,926,000	5,234,000	5,126,000
Line of credit facility, repayments						$ 38,075,000
Number of real estate properties disposed | Property						2
Exit fees pursuant to contractual terms of the mortgage indebtedness						$ 486,000
Interest received						361,000	$ 965,000	$ 966,000
IRT | Consolidation Eliminations | Fees and Other Income
Related Party Transaction [Line Items]
Earned asset management fees						$ 5,584,000
IRT | Maximum
Related Party Transaction [Line Items]
Management fee percentage						4.00%
IRT | If IROP Elects to Extend its Maturity | Maximum
Related Party Transaction [Line Items]
Cumulative gross amount of equity capital, hurdle rate				1.75%
Cumulative gross amount of equity capital, annual hurdle rate				7.00%
IRT | If Pre-incentive Fee Core FFO Exceeds Hurdle Rate
Related Party Transaction [Line Items]
Advisor incentive fee				20.00%
IRT | If Pre-incentive Fee Core FFO Exceeds Hurdle Rate | Minimum
Related Party Transaction [Line Items]
Cumulative gross amount of equity capital, hurdle rate				1.75%
Cumulative gross amount of equity capital, annual hurdle rate				7.00%