Equity - Additional Information (Details) - USD ($)								1 Months Ended	3 Months Ended		6 Months Ended
	Jul. 14, 2016	Jul. 07, 2016	May 04, 2016	May 02, 2016	Apr. 07, 2016	Jan. 07, 2016	Jul. 10, 2015	May 31, 2015	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Class of Stock
Authorized capital shares of common stock (in shares)									500,000,000		500,000,000		500,000,000
Authorized capital shares of preferred stock (in shares)									100,000,000		100,000,000		100,000,000
Common stock, shares issued (in shares)									32,825,063		32,825,063		30,076,359
Common stock, shares outstanding (in shares)									32,825,063		32,825,063		30,076,359
Preferred stock issued (in shares)									0		0		0
Preferred stock outstanding (in shares)									0		0		0
Percentage of Operating Partnership held (as a percent)									65.50%		65.50%		65.60%
Aggregate cash dividends and distributions, paid											$ 15,873,000	$ 13,144,000
Cash dividend per share, declared (in dollars per share)									$ 0.18	$ 0.17	$ 0.18	$ 0.17
Class A units
Class of Stock
Class A Units not held by Company (in shares)									16,322,171		16,322,171
Dividend Declared
Class of Stock
Cash dividend per share, declared (in dollars per share)				$ 0.18
Common Stock
Class of Stock
Shares issued through public offering (in shares)											2,649,986
Common stock, shares outstanding (in shares)									32,825,063		32,825,063		30,076,359
Aggregate cash dividends and distributions, paid					$ 5,600,000	$ 5,100,000
Common Stock | Subsequent Event
Class of Stock
Aggregate cash dividends and distributions, paid		$ 5,900,000
Operating Partnership | Class A units
Class of Stock
Aggregate cash dividends and distributions, paid					$ 2,700,000	$ 2,500,000
Operating Partnership | Class A units | Subsequent Event
Class of Stock
Aggregate cash dividends and distributions, paid		$ 2,900,000
Operating Partnership | Columbus Village | Class B units
Class of Stock
Acquisition, common units/shares issued or to be issued (in shares)							1,000,000
Operating Partnership | Columbus Village | Class C units
Class of Stock
Acquisition, common units/shares issued or to be issued (in shares)							275,000
New ATM Program | Common Stock
Class of Stock
Maximum aggregate offering price of shares to be sold (up to)			$ 75,000,000.0
Shares issued through public offering (in shares)											1,497,067
Net proceeds after offering costs and commissions from sale of shares											$ 18,200,000
Numbers shares issued and sold, weighted average price per share (in dollars per share)									$ 12.45		$ 12.45
New ATM Program | Common Stock | Subsequent Event
Class of Stock
Shares issued through public offering (in shares)	676,903
Net proceeds after offering costs and commissions from sale of shares	$ 9,200,000
Numbers shares issued and sold, weighted average price per share (in dollars per share)	$ 13.81
Prior ATM Program | Common Stock
Class of Stock
Maximum aggregate offering price of shares to be sold (up to)								$ 50,000,000.0
Shares issued through public offering (in shares)											1,512,919
Net proceeds after offering costs and commissions from sale of shares											$ 12,200,000
Numbers shares issued and sold, weighted average price per share (in dollars per share)									$ 10.87		$ 10.87