Organization and Offering (Narratives) (Details) (USD $)	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2013	Mar. 31, 2013 property tenant sqft	Dec. 31, 2012
Business and Organization
Number of Real Estate Properties		338
Number Of Tenants		82
Square footage of real estate property		32,000,000
Number of self storage properties		59
Square footage of self storage properties		4,000,000
Operating Partnership Interest		99.985%
Percentage Of General And Limited Partnership Interest		0.015%
Public Offerings [Abstract]
Proceeds from Issuance Follow On Offering, Shares	289,000,000
Proceeds from Issuance Follow On Offering, Value	$ 2,900,000,000	$ 22,749,000	$ 903,229,000
Shares Issued From Drip in Follow On Public Offering		20,050,275
Proceeds From Issuance Drip Follow On Public Offering		190,500,000
Stock Repurchased During Period Shares		4,196,724
Stock Repurchased During Period Value		$ 39,500,000
Total Shares Authorized	950,000,000
Common Stock Shares Authorized	900,000,000	900,000,000
Common Stock Par Or Stated Value Per Share	$ 0.001	$ 0.001
Preferred Stock Shares Authorized	50,000,000	50,000,000
Preferred Stock Par Or Stated Value Per Share	$ 0.001	$ 0.001
Total Shares Authorized For Dividend Reinvestment Plan	200,000,000