Indebtedness (Tables)

9 Months Ended

Sep. 30, 2012

Debt Disclosure [Abstract]

Fair Value, Liabilities Measured on a Recurring Basis, Disclosure Only

	Book Value at 12/31/11		Book Value at 9/30/12		Fair Value at 12/31/11		Issuances and Assumptions		Payments/Payoffs			Adjustments to Fair Value		Fair Value at 9/30/12
Fixed rate secured debt	$	1,167,188	$	1,077,991	$	1,256,331	$	18,741	$	(106,355	)	$	6,147	$	1,174,864
Variable rate secured debt	6,045		18,464		6,045		13,305		(885		)	499		18,964
Unsecured notes	2,616,063		3,043,690		2,834,610		600,000		(172,374		)	150,385		3,412,621
Unsecured lines of credit	20,293		—		20,244		—		(20,293		)	49		—
Total	$	3,809,589	$	4,140,145	$	4,117,230	$	632,046	$	(299,907	)	$	157,080	$	4,606,449

Unsecured Lines of Credit

Description	Maximum Capacity		Maturity Date	Outstanding Balance at September 30, 2012
Unsecured Line of Credit - Partnership	$	850,000	December 2015	$	—