Schedule III - Real Estate and Accumulated Depreciation (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Real Estate and Accumulated Depreciation [Line Items]
Total real estate held for investment, beginning of year	$ 3,798,690		$ 3,216,871		$ 2,520,083
Acquisitions	1,023,384		617,923		643,776
Improvements, etc.	207,345		84,736		86,754
Total additions during period	1,230,729		702,659		730,530
Cost of real estate sold	(264,533)		(21,052)		(17,456)
Properties held for sale	0		(89,937)		0
Other	(7,492)	[1]	(9,851)	[1]	(16,286)	[1]
Total deductions during period	(272,025)		(120,840)		(33,742)
Total real estate held for investment, end of year	$ 4,757,394		$ 3,798,690		$ 3,216,871

[1] Related to the redevelopment property transferred to construction in progress during the year.