Subsequent Events (Details) (USD $)	3 Months Ended	0 Months Ended	12 Months Ended		3 Months Ended
	Mar. 30, 2015 member	Jan. 22, 2015	Dec. 31, 2014 property building sqft		Mar. 27, 2015 building sqft		Feb. 06, 2014
Subsequent Event [Member]
Purchase Price of Acquisitions [Roll Forward]
Number of board of director members being recruited	2
Unsecured Debt [Member] | 2% 2017 Notes [Member]
Purchase Price of Acquisitions [Roll Forward]
Interest rate, stated percentage							2.00%
Unsecured Debt [Member] | 3% 2019 Notes [Member]
Purchase Price of Acquisitions [Roll Forward]
Interest rate, stated percentage							3.00%
Unsecured Debt [Member] | 4.6% 2024 Notes [Member]
Purchase Price of Acquisitions [Roll Forward]
Interest rate, stated percentage							4.60%
Senior Notes [Member] | Subsequent Event [Member]
Purchase Price of Acquisitions [Roll Forward]
Consideration associated with agreement not to issue debt default (up to $300,000)		$ 300,000
Cure period		60 days
Cure period reduction		1 day
2014 Acquisitions [Member]
Number of Buildings [Roll Forward]
Number of properties acquired			1,107
Number of buildings, ending balance			4,648
Area of Acquisitions [Roll Forward]
Square feet of property, ending balance			103,149,000
Purchase Price of Acquisitions [Roll Forward]
Base purchase price, ending balance			17,849,621,000	[1]
2014 Acquisitions [Member] | Subsequent Event [Member]
Number of Buildings [Roll Forward]
Number of properties acquired					5
Number of buildings, ending balance					4,653
Area of Acquisitions [Roll Forward]
Square feet, acquisitions					(1,137,000)
Square feet of property, ending balance					102,012,000
Purchase Price of Acquisitions [Roll Forward]
Base purchase price, acquisitions					(286,112,000)	[1]
Base purchase price, ending balance					$ 17,563,509,000	[1]

[1] Contract purchase price, excluding acquisition and transaction related costs.