Schedule of Revenue and Net Income (Loss) Allocable to Common Shares for the Properties Acquired (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Real Estate Properties [Line Items]
Total Revenue	$ 15,012	$ 29,614	$ 52,023	$ 89,335
Net income (loss) allocable to common shares	(24,230)	$ (4)	(180,072)	$ (25,428)
Properties Acquired
Real Estate Properties [Line Items]
Total Revenue	380		833
Net income (loss) allocable to common shares	(107)		(231)
Properties Acquired | Erieview Galleria
Real Estate Properties [Line Items]
Total Revenue	380		833
Net income (loss) allocable to common shares	$ (107)		$ (231)