Equity - Change in Net Income Attributable to Common Shareholders (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class of Stock [Line Items]
Net income attributable to common stockholders	$ 9,768	$ 9,985
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	19,930	17,796
Additional Paid-In Capital
Class of Stock [Line Items]
Increase in additional paid-in capital for the conversion of OP Units into common stock	$ 10,162	$ 7,811