Summary Of Activity In Storage Facilities (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012
Schedule Of Investments In Real Estate [Line Items]
Cost: Beginning balance	$ 1,538,595
Acquisition of storage facilities	104,257
Improvements and equipment additions	24,371
Net decrease in construction in progress	(3,192)
Dispositions and impairments	(1,118)
Cost: Ending balance	1,662,913
Accumulated Depreciation: Beginning balance	292,722
Depreciation expense during the period	27,661
Dispositions	(442)
Accumulated Depreciation: Ending balance	$ 319,941