Summary of Significant Accounting Policies - Additional Information (Detail) - $ / shares			6 Months Ended
	Jun. 16, 2015	Jan. 15, 2015	Jun. 30, 2015	Jun. 30, 2014
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Quarterly dividend paid per Common Share				$ 0.1625
Liquidation distribution per share	$ 1.25	$ 2.25	$ 15.23
Series D Preferred Shares of Beneficial Interest [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Quarterly dividend paid per Series D Preferred Share				$ 0.578125