Subsequent Events (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			1 Months Ended
	Mar. 31, 2014 property	Mar. 31, 2013 property	Mar. 31, 2014 2014 Acquisitions [Member] sqft property	May 07, 2014 Subsequent Event [Member] sqft property	May 07, 2014 Subsequent Event [Member] 2014 Acquisitions [Member] property sqft
Subsequent Event [Line Items]
Number of owned properties			3,809		3,834
Number of properties acquired	215	112		25
Square feet of property			101,800,000		102,800,000
Square Feet, Acquisitions				1,000,000
Base Purchase Price			$ 17,961		$ 18,072
Base Purchase Price, Acquisitions				$ 111