Equity - Additional Information (Details)																										1 Months Ended	8 Months Ended	12 Months Ended
	Feb. 02, 2017 $ / shares	Jan. 10, 2017 shares	Jan. 05, 2017 USD ($)	Nov. 03, 2016 $ / shares	Oct. 13, 2016 USD ($) shares	Aug. 04, 2016 $ / shares	May 04, 2016 USD ($)	May 02, 2016 $ / shares	Jan. 31, 2016 $ / shares	Dec. 09, 2015 USD ($) shares	Nov. 06, 2015 $ / shares	Aug. 06, 2015 $ / shares	Jul. 10, 2015 shares	May 08, 2015 $ / shares	May 05, 2015 USD ($)	Apr. 08, 2015 shares	Jan. 28, 2015 $ / shares	Nov. 10, 2014 $ / shares	Sep. 15, 2014 USD ($) shares	Aug. 15, 2014 shares	Aug. 04, 2014 $ / shares	May 09, 2014 $ / shares	Mar. 31, 2014 shares	Feb. 18, 2014 $ / shares	Jan. 17, 2014 shares	May 31, 2015 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares	Dec. 31, 2013 shares
Class of Stock [Line Items]
Authorized capital shares of common stock (in shares)																											500,000,000	500,000,000	500,000,000
Preferred stock, shares authorized (in dollars per share)																											100,000,000	100,000,000	100,000,000
Common stock, shares issued (in shares)																											37,490,361	37,490,361	30,076,359
Common stock, shares outstanding (in shares)																											37,490,361	37,490,361	30,076,359
Preferred stock, shares issued (in dollars per share)																											0	0	0
Preferred stock, shares outstanding (in dollars per share)																											0	0	0
Acquisition, common units/shares issued (in shares)					2,000,000
Shares issued through public offering (in shares)										3,450,000									5,750,000
Acquisition, contract price | $					$ 26,200,000
Net proceeds from public offering | $										$ 35,100,000									$ 49,300,000									$ 68,475,000	$ 46,462,000	$ 49,566,000
Percentage of operating partnerships held																											68.10%	68.10%	65.60%
Operating partnership units redemption ratio																												1
Aggregate cash dividends and distributions, paid | $																												$ 33,843,000	$ 27,024,000	$ 22,096,000
Cash dividend per share, declared (in dollars per share) | $ / shares				$ 0.18		$ 0.18		$ 0.18	$ 0.18		$ 0.17	$ 0.17		$ 0.17			$ 0.17	$ 0.16			$ 0.16	$ 0.16		$ 0.16				$ 0.72	$ 0.68	$ 0.64
Dividend Declared | Subsequent Event
Class of Stock [Line Items]
Cash dividend per share, declared (in dollars per share) | $ / shares	$ 0.19
Operating Partnership
Class of Stock [Line Items]
Aggregate cash dividends and distributions, paid | $																														$ 8,900,000
Town Center Phase VI | Subsequent Event
Class of Stock [Line Items]
Ownership interest percentage in properties		20.00%
Class A units | Operating Partnership
Class of Stock [Line Items]
Aggregate cash dividends and distributions, paid | $																												$ 11,100,000	$ 9,900,000
Class A units | Operating Partnership | Subsequent Event
Class of Stock [Line Items]
Aggregate cash dividends and distributions, paid | $			$ 3,000,000
Class A units | Town Center Phase VI | Subsequent Event
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)		68,691
Common stock
Class of Stock [Line Items]
Common stock, shares outstanding (in shares)																											37,490,361	37,490,361	30,076,359	25,022,701	19,163,413
Shares issued through public offering (in shares)																												5,312,855	4,560,049	5,750,000
Aggregate cash dividends and distributions, paid | $																												$ 22,700,000	$ 17,100,000	$ 13,200,000
Common stock | Subsequent Event
Class of Stock [Line Items]
Aggregate cash dividends and distributions, paid | $			$ 6,700,000
Columbus Village | Class B units
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)													1,000,000
Columbus Village | Class C units
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)													275,000
Columbus Village | Class C units | Subsequent Event
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)		275,000
Liberty Apartments | Class A units
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)																									695,652
Sandbridge Commons | Class A units
Class of Stock [Line Items]
Common units in exchange for all noncontrolling interests (in shares)																							30,000
Dimmock Square
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)																				990,952
Dimmock Square | Class A units
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)																				990,952
Private Placement | Perry Hall Marketplace
Class of Stock [Line Items]
Acquisition, common units/shares issued (in shares)																415,500
Continuous Equity Program
Class of Stock [Line Items]
Maximum aggregate offering price of shares to be sold (up to) | $															$ 50,000,000.0
Shares issued through public offering (in shares)																													1,108,149
Numbers shares issued and sold, weighted average price per share (in dollars per share) | $ / shares																													$ 10.26
Net proceeds after offering costs and commissions from sale of shares | $																													$ 10,900,000
Continuous Equity Program | Common stock
Class of Stock [Line Items]
Maximum aggregate offering price of shares to be sold (up to) | $							$ 75,000,000.0
Shares issued through public offering (in shares)																											4,159,936
Numbers shares issued and sold, weighted average price per share (in dollars per share) | $ / shares																											$ 13.45	$ 13.45
Net proceeds after offering costs and commissions from sale of shares | $																											$ 54,800,000
Prior Equity Program | Common stock
Class of Stock [Line Items]
Shares issued through public offering (in shares)																										1,152,919
Numbers shares issued and sold, weighted average price per share (in dollars per share) | $ / shares																										$ 10.87
Net proceeds after offering costs and commissions from sale of shares | $																										$ 12,200,000