Summary of Significant Accounting Policies and Procedures and Recent Accounting Pronouncements - Discontinued Operations, Revenue Recognition, Accounts Receivable (Details)	12 Months Ended
	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares
Summary of Significant Accounting Policies and Procedures and Recent Accounting Pronouncements
Number of investment properties classified as held for sale, reported as discontinued operations | item	10
Amount of debt assumed by buyers of investment properties, or repaid as a result of investment property sales	$ 0
Income from discontinued operations
Income from discontinued operations		$ 2,800,000	$ 65,670,000
Per common share, basic and diluted (in dollars per share) | $ / shares		$ 0.01	$ 0.34
Revenue Recognition and Accounts Receivable
Allowance for Doubtful Accounts Receivable	429,000	$ 765,000
Other Real Estate Revenue	$ 4,405,000	$ 2,930,000	$ 7,047,000