Mortgage Note Payable (Schedule of Mortgage Notes Payable) (Details) (USD $)	3 Months Ended
	Mar. 31, 2014 property		Mar. 31, 2013		Dec. 31, 2013 property
Mortgage Loans on Real Estate [Line Items]
Outstanding Loan Amount	$ 4,234,668,000				$ 1,301,114,000
Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Encumbered Properties	697				177
Outstanding Loan Amount	4,128,384,000				1,258,661,000
Weighted Average Effective Interest Rate	4.83%	[1]			3.42%	[1]
Weighted Average Maturity	6 years 2 months 23 days	[2]	3 years 4 months 28 days	[2]
Long-term debt, defeased	721,710,210
Long-term debt, defeased, prepayments and swap breakage fee	29,814,987
Payment to settle interest rate swaps	9,900,000
Write off of deferred debt issuance cost	22,000,000
CapLease [Member]
Mortgage Loans on Real Estate [Line Items]
Mortgages assumed in real estate acquisitions	137,400,000
Debt instrument, unamortized discount (premium), net	$ 106,300,000
Minimum [Member] | Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate	2.41%				1.83%
Maximum [Member] | Mortgages [Member]
Mortgage Loans on Real Estate [Line Items]
Effective interest rate	7.20%				6.28%

[1] Mortgage notes payable primarily have fixed rates or are fixed by way of interest rate swap arrangements. Effective interest rates range from 2.41% to 7.20% at March 31, 2014 and 1.83% to 6.28% at December 31, 2013.

[2] Weighted average remaining years until maturity as of March 31, 2014 and December 31, 2013, respectively.