Investments In Real Estate (Narrative) (Details)	3 Months Ended		9 Months Ended			0 Months Ended		3 Months Ended		9 Months Ended		6 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Dec. 31, 2011 USD ($)	Jul. 11, 2012 Sentrum Portfolio [Member] USD ($) sqft	Jul. 11, 2012 Sentrum Portfolio [Member] GBP (£)	Sep. 30, 2012 Sentrum Portfolio [Member] USD ($)		Sep. 30, 2012 Sentrum Portfolio [Member] USD ($)		Jun. 30, 2012 Savvis Joint Venture Property, Hong Kong [Member] USD ($)	Jun. 26, 2012 Savvis Joint Venture Property, Hong Kong [Member] sqft
Business Acquisition [Line Items]
Acquisition, Date Acquired						Jul. 11, 2012	Jul. 11, 2012			Jul. 11, 2012	[1]	Jun. 26, 2012
Square footage of real estate property						733,000	733,000						164,000
Acquisition, Amount	$ 1,462,200,000		$ 1,462,200,000			$ 1,100,000,000	£ 734,600,000	$ 1,138,600,000	[1]	$ 1,138,600,000	[1]	$ 20,600,000
Acquisition allocation to land						18,100,000
Acquisition allocation to ground leases						7,000,000
Acquisition allocation to buildings and improvements						1,200,000,000
Acquisition allocation to tenant improvements						11,600,000
Acquisition allocation to intangible assets						151,600,000
Acquired in place lease value, Net	492,393,000		492,393,000		335,381,000	107,200,000
Acquired above market leases, Net	68,269,000		68,269,000		29,701,000	44,400,000
Acquisition allocation to intangible liabilities						38,200,000
Operating revenue	342,479,000	273,476,000	929,331,000	792,098,000				28,400,000		28,400,000
Operating income	$ 97,075,000	$ 71,626,000	$ 271,440,000	$ 223,011,000				$ 6,800,000		$ 6,800,000

[1] On July 11, 2012, we completed the acquisition of a three-property data center portfolio, totaling approximately 733,000 square feet, located in the greater London area, referred to as the Sentrum Portfolio. The purchase price was £734.6 million (equivalent to approximately $1.1 billion based on the July 11, 2012 exchange rate of £1.00 to $1.55), which includes an £18.7 million (equivalent to approximately $29.0 million based on the July 11, 2012 exchange rate of £1.00 to $1.55) adjustment in the purchase price to reflect amounts associated with the early repayment of property debt. In addition, non-cash consideration of £56.5 million (or $87.6 million based on the July 11, 2012 exchange rate of £1.00 to $1.55) was recorded as the expected fair value of contingent consideration as required by prevailing accounting guidance. There was also a non-cash purchase adjustment related to deferred taxes, which amounted to £68.6 million (or $106.3 million based on the July 11, 2012 exchange rate of £1.00 to $1.55). The purchase price was paid in cash funded with proceeds from our common stock offering in July 2012 along with borrowings under our global revolving credit facility.