Annual report pursuant to Section 13 and 15(d)

Investment In Storage Facilities (Narrative) (Details)

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Investment In Storage Facilities (Narrative) (Details) (USD $)
In Millions, unless otherwise specified
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2011
In-Place Customer Leases [Member]
Dec. 31, 2010
In-Place Customer Leases [Member]
Dec. 31, 2009
In-Place Customer Leases [Member]
Finite-Lived Intangible Assets [Line Items]          
Amortization period for in-place customer leases on a straight-line basis (in months)     12    
Amortization expense related to in-place customer leases     $ 1.6 $ 0 $ 0.3
Number of Properties 29 7      
Amortization expense in 2012 $ 2.5