Real Estate Properties - Pro Forma (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Rental income	$ 328,255
Net loss	$ (4,733)
Net loss per share (in dollars per share) | $ / shares	$ (0.05)
Acquisition-related costs
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Decrease in revenues	$ 804
Decrease in net income	$ 47,019