Equity - Change in Net Income Attributable to Common Shareholders (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Class of Stock [Line Items]
Net income attributable to common stockholders	$ 16,651	$ 16,584	$ 26,419	$ 26,569
Increase in additional paid-in capital for the conversion of OP Units into common stock			0
Change from net income attributable to common stockholders and transfers from non-controlling interests	32,329	17,907	52,259	35,703
Additional Paid-In Capital
Class of Stock [Line Items]
Increase in additional paid-in capital for the conversion of OP Units into common stock	$ 15,678	$ 1,323	$ 25,840	$ 9,134