Shareholders' Equity - Additional Information (Detail) - USD ($)									3 Months Ended		6 Months Ended
	Apr. 29, 2016	Apr. 22, 2016	Mar. 14, 2016	Feb. 23, 2016	Feb. 22, 2016	Feb. 12, 2016	Sep. 17, 2015	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015	Sep. 30, 2015	Dec. 31, 2015	Jun. 13, 2014	Nov. 21, 2012
Class of Stock [Line Items]
Common stock, dividend declared			$ 0.09
Common stock, dividend paid									$ 8,548,000
Annual incentive compensation plan description									On March 31, 2015, the compensation committee adopted a 2015 Annual Incentive Compensation Plan, or the annual cash bonus plan, and made awards to three of our executive officers, or the eligible officers, setting forth the basis on which 2015 target cash bonus awards are earned. In addition, the compensation committee adopted a 2015 Long Term Incentive Plan, or the LTIP, and made awards, or the 2015 awards, to the eligible officers setting forth the basis on which the eligible officers could earn equity compensation for the years 2015 through 2018. Pursuant to the LTIP, each eligible officer was granted an initial long term equity award, consisting of both a performance share unit award for a three year performance period and an annual restricted share award vesting over a four year period. Three components of the performance share unit award have market conditions and had grant date fair values of $3.35, $3.26 and $2.17 per share. Both the annual cash bonus plan and the LTIP were adopted pursuant to our 2012 Incentive Award Plan. For the three months ended March 31, 2016, we recorded $122 of compensation expense related to the LTIP.
Compensation expense									$ 7,075,000	$ 6,108,000
Common shares pursuant to the DRSPP									2,527
Net proceeds received									$ 6,000
Common shares remaining available under the DRSPP									7,759,195
Jones Trading Institutional Services LLC
Class of Stock [Line Items]
Common shares, shares issued									0
Common shares remaining available for issuance									7,918,919
Jones Trading Institutional Services LLC | Maximum
Class of Stock [Line Items]
Common shares to be issued and sold														10,000,000
IRT
Class of Stock [Line Items]
Shares outstanding									7,269,719			7,269,719
Ownership percentage									15.40%			15.50%
IRT | Trade Street Residential, Inc
Class of Stock [Line Items]
Common stock issued in connection with merger							15,110,994
IROP | Trade Street Residential, Inc
Class of Stock [Line Items]
Common stock issued in connection with merger							1,925,419
Long Term Incentive Compensation Plan Ltip
Class of Stock [Line Items]
Compensation expense											$ 122,000
Short Term Annual Cash Bonus Plan | Tranche One
Class of Stock [Line Items]
Percentage of target awards payable										75.00%
Percentage of cash available for distribution										35.00%
Percentage of adjusted book value										20.00%
Percentage of return on equity										20.00%
Short Term Annual Cash Bonus Plan | Tranche Two
Class of Stock [Line Items]
Percentage of target awards payable										25.00%
Short Term Annual Cash Bonus Plan | Minimum Performance Target
Class of Stock [Line Items]
Target incentive opportunity payable percentage										50.00%
Short Term Annual Cash Bonus Plan | Target Performance Target
Class of Stock [Line Items]
Target incentive opportunity payable percentage										100.00%
Short Term Annual Cash Bonus Plan | Maximum Performance Target
Class of Stock [Line Items]
Target incentive opportunity payable percentage										150.00%
LTIP | Performance Based Long Term Incentive Plan
Class of Stock [Line Items]
Vesting period								3 years
Compensation awarded, Percentage of award								75.00%
LTIP | Time Based Long Term Incentive Plan
Class of Stock [Line Items]
Vesting period								3 years
Compensation awarded, Percentage of award								25.00%
LTIP | Peer Group of Public Companies Over The Same Period
Class of Stock [Line Items]
Equity award target percentage								40.00%
LTIP | TSR for the NAREIT Mortgage Index
Class of Stock [Line Items]
Equity award target percentage								20.00%
LTIP | Absolute TSR
Class of Stock [Line Items]
Equity award target percentage								20.00%
LTIP | Strategic Objective
Class of Stock [Line Items]
Equity award target percentage								20.00%
Non-management trustees
Class of Stock [Line Items]
Number of shares awarded, share				168,776
Number of shares awarded, value				$ 400,000
Closing stock price				$ 2.37
Vesting period				3 years
Subsequent Event
Class of Stock [Line Items]
Common stock, dividend paid	$ 8,200,000
Restricted Stock
Class of Stock [Line Items]
Common stock, dividend paid									$ 348,000
Restricted Stock | IRT
Class of Stock [Line Items]
Number of shares awarded, value						$ 1,306,000
Closing stock price						$ 6.22
Vesting period						3 years
Number of shares awarded, share						210,000
Restricted Stock | Non Executive Officer
Class of Stock [Line Items]
Number of shares awarded, share					367,000
Number of shares awarded, value					$ 873,000
Closing stock price					$ 2.38
Vesting period					3 years
Restricted Stock | Subsequent Event
Class of Stock [Line Items]
Vesting period		4 years
Stock Appreciation Rights (SARs) | Non Executive Officer
Class of Stock [Line Items]
Number of shares awarded, share					895,000
Number of shares awarded, value					$ 206,000
Vesting period					3 years
Expiration date					Feb. 22, 2021
Performance Shares Component One | Long Term Incentive Compensation Plan Ltip
Class of Stock [Line Items]
Grant date fair value per share									$ 3.35
Performance Shares Component Two | Long Term Incentive Compensation Plan Ltip
Class of Stock [Line Items]
Grant date fair value per share									3.26
Performance Shares Component Three | Long Term Incentive Compensation Plan Ltip
Class of Stock [Line Items]
Grant date fair value per share									$ 2.17
Performance Shares | Subsequent Event
Class of Stock [Line Items]
Performance period		3 years
Performance period earliest date		Jan. 01, 2016
Performance period latest date		Dec. 31, 2018
Dividend Reinvestment And Share Purchase Plan
Class of Stock [Line Items]
Registered and reserved common shares									10,500,000
Weighted-average price per shares									$ 2.56
Preferred Stock
Class of Stock [Line Items]
Preferred shares aggregate amount to be issued and sold													$ 150,000,000
Preferred Stock | 7.75% Series A Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred shares authorized to be issued under agreement													4,000,000
Dividend payment date									Mar. 31, 2016
Dividend record date									Mar. 01, 2016
Preferred Stock | 8.375% Series B Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred shares authorized to be issued under agreement													1,000,000
Dividend payment date									Mar. 31, 2016
Dividend record date									Mar. 01, 2016
Preferred Stock | 8.875% Series C Cumulative Redeemable Preferred Stock
Class of Stock [Line Items]
Preferred shares authorized to be issued under agreement													1,000,000
Dividend payment date									Mar. 31, 2016
Dividend record date									Mar. 01, 2016
Preferred Stock | 7.75% Series A cumulative redeemable preferred shares
Class of Stock [Line Items]
Aggregate of Series A,B,C Preferred Shares available for issuance									2,763,204
Preferred Stock | 8.375% Series B cumulative redeemable preferred shares
Class of Stock [Line Items]
Aggregate of Series A,B,C Preferred Shares available for issuance									947,496
Preferred Stock | 8.875% Series C cumulative redeemable preferred shares
Class of Stock [Line Items]
Aggregate of Series A,B,C Preferred Shares available for issuance									999,675
Common Shares
Class of Stock [Line Items]
Dividend payment date			Apr. 29, 2016
Dividend record date			Apr. 08, 2016
Common shares, shares issued									2,527