Equity - Additional Information (Details) - USD ($)							1 Months Ended	3 Months Ended
	May 07, 2019	Apr. 04, 2019	Feb. 21, 2019	Jan. 03, 2019	Jan. 02, 2019	Feb. 26, 2018	Apr. 30, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Class of Stock
Authorized capital shares of common stock (in shares)								500,000,000		500,000,000
Authorized capital shares of preferred stock (in shares)								100,000,000		100,000,000
Common stock, shares issued (in shares)								52,326,803		50,013,731
Common stock, shares outstanding (in shares)								52,326,803		50,013,731
Preferred stock issued (in shares)								0		0
Preferred stock outstanding (in shares)								0		0
Percentage of Operating Partnership held								75.50%		74.50%
Aggregate cash dividends and distributions, paid								$ 13,447,000	$ 11,808,000
Dividends and distributions declared per common share and unit (in dollars per share)			$ 0.21					$ 0.21	$ 0.20
Class A units
Class of Stock
Class A Units not held by Company (in shares)								16,991,933
Class A units | Operating Partnership
Class of Stock
Aggregate cash dividends and distributions, paid				$ 3,400,000
Common Stock
Class of Stock
Common stock, shares outstanding (in shares)								52,326,803	45,205,575	50,013,731	44,937,763
Shares issued (in shares)					118,471			2,071,000
Aggregate cash dividends and distributions, paid				$ 10,000,000
New ATM Program
Class of Stock
Consideration received on transaction								$ 30,200,000
New ATM Program | Common Stock
Class of Stock
Maximum aggregate offering price of shares to be sold (up to)						$ 125,000,000
Shares issued (in shares)								2,071,000
Weighted average price (in dollars per share)								$ 14.78
Subsequent Event
Class of Stock
Dividends and distributions declared per common share and unit (in dollars per share)	$ 0.21
Subsequent Event | Class A units | Operating Partnership
Class of Stock
Aggregate cash dividends and distributions, paid		$ 3,600,000
Subsequent Event | Common Stock
Class of Stock
Aggregate cash dividends and distributions, paid		$ 11,000,000
Subsequent Event | New ATM Program
Class of Stock
Consideration received on transaction							$ 1,400,000
Subsequent Event | New ATM Program | Common Stock
Class of Stock
Shares issued (in shares)							91,924
Weighted average price (in dollars per share)							$ 15.72
Consolidated Entities Under Development Or Construction | Operating Partnership
Class of Stock
Ownership interest percentage in properties								$ 0		$ 0