Acquisitions and Dispositions - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenue	$ 405,320	$ 352,432
Net income	42,149	39,233
Net income available to common shareholders	$ 39,759	$ 35,614
Earnings per share basic (in dollars per share)	$ 0.24	$ 0.22
Earnings per share diluted (in dollars per share)	$ 0.24	$ 0.22
Weighted average number of shares outstanding - basic (in shares)	163,123,109	163,123,109
Weight average number of shares outstanding - diluted (in shares)	168,231,299	168,231,299
Operating Partnership
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenue	$ 405,320	$ 352,432
Net income	42,149	39,233
Net income available to common shareholders	$ 40,927	$ 36,660
Earnings per unit basic (in dollars per share)	$ 0.24	$ 0.22
Earnings per unit diluted (in dollars per share)	$ 0.24	$ 0.22
Weighted average limited partnership units outstanding, basic (in shares)	167,963,076	167,963,076
Weighted average number of units outstanding - diluted (in shares)	168,231,299	168,231,299