Discontinued Operations and Gain on Disposition of Rental Properties (Details)	3 Months Ended
	Apr. 30, 2012 sqft	Apr. 30, 2011
Quebec Square [Member]
Summary of rental properties included in discontinued operations
Location	Denver, Colorado
Square Feet	739,000
Period Disposed	Q1-2012
Period Status	Yes	Yes
Ritz-Carlton hotel [Member]
Summary of rental properties included in discontinued operations
Location	Cleveland, Ohio
Number of units/Rooms	206
Period Disposed	Q4-2011
Period Status		Yes
250 Huron (Office Building) [Member]
Summary of rental properties included in discontinued operations
Location	Cleveland, Ohio
Square Feet	119,000
Period Disposed	Q4-2011
Period Status		Yes
Waterfront Station - East 4th & West 4th Buildings [Member]
Summary of rental properties included in discontinued operations
Location	Washington, D.C.
Square Feet	631,000
Period Disposed	Q2-2011
Period Status		Yes
Charleston Marriott hotel [Member]
Summary of rental properties included in discontinued operations
Location	Charleston, West Virginia
Number of units/Rooms	352
Period Disposed	Q1-2011
Period Status		Yes