Fair Value Measurements (Details) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended			6 Months Ended	12 Months Ended																									3 Months Ended		6 Months Ended		12 Months Ended				6 Months Ended		12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended		12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 3 [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member]	Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member]	Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Estimate of Fair Value, Fair Value Disclosure [Member]		Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Estimate of Fair Value, Fair Value Disclosure [Member]		Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member]		Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 1 [Member]		Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]		Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 2 [Member]		Jun. 30, 2012 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]		Dec. 31, 2011 Fair Value, Measurements, Nonrecurring [Member] Fair Value, Inputs, Level 3 [Member]		Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Estimate of Fair Value, Fair Value Disclosure [Member]	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 1 [Member]	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 2 [Member]	Jun. 30, 2012 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2011 Fair Value, Measurements, Recurring [Member] Fair Value, Inputs, Level 3 [Member]	Sep. 30, 2012 Blackstone Portfolio [Member]	Jun. 30, 2012 Blackstone Portfolio [Member]	Jun. 30, 2012 Long Lived Assets Held And Used [Member] Fair Value, Measurements, Nonrecurring [Member]		Dec. 31, 2011 Long Lived Assets Held And Used [Member] Fair Value, Measurements, Nonrecurring [Member]		Dec. 31, 2011 Equity Method Investments [Member] Fair Value, Measurements, Nonrecurring [Member]		Jun. 30, 2012 Minimum Notes Receivable [Member]	Jun. 30, 2012 Minimum Yield rates	Dec. 31, 2011 Minimum Yield rates	Jun. 30, 2012 Minimum Rental growth rates	Dec. 31, 2011 Minimum Rental growth rates	Jun. 30, 2012 Minimum Discount rates	Dec. 31, 2011 Minimum Discount rates	Jun. 30, 2012 Minimum Terminal cap rates	Dec. 31, 2011 Minimum Terminal cap rates	Jun. 30, 2012 Maximum Notes Receivable [Member]	Jun. 30, 2012 Maximum Yield rates	Dec. 31, 2011 Maximum Yield rates	Jun. 30, 2012 Maximum Rental growth rates	Dec. 31, 2011 Maximum Rental growth rates	Jun. 30, 2012 Maximum Discount rates	Dec. 31, 2011 Maximum Discount rates	Jun. 30, 2012 Maximum Terminal cap rates	Dec. 31, 2011 Maximum Terminal cap rates	Jun. 30, 2012 Line of Credit Facility - Unsecured [Member] Minimum	Jun. 30, 2012 Notes Payable, Other Payables [Member] Minimum	Jun. 30, 2012 Notes Payable, Other Payables [Member] Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Ratios Related To Real Estate Fair Value Inputs																																									8.50%	7.50%	0.00%	2.00%	0.00%	8.50%	0.00%	8.00%		8.50%	9.00%	0.00%	3.00%	0.00%	10.00%	0.00%	9.50%
Property, Plant, and Equipment, Fair Value Disclosure								$ 325,693,000	[1]	$ 5,520,000	[2]	$ 0	[1]	$ 0	[2]	$ 320,682,000	[1]	$ 0	[2]	$ 5,011,000	[1]	$ 5,520,000	[2]
Proceeds from Sale of Real Estate		39,200,000																														321,000,000
Disposal Date																																July 25, 2012
Equity Method Investment, Other than Temporary Impairment																																						(4,580,000)	[2]
Fair Value, Option, Changes in Fair Value, Gain (Loss)						(23,000,000)	(16,423,000)																											(23,000,000)	[1]	(11,843,000)	[2]
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures										1,893,000	[2]			0	[2]			0	[2]			1,893,000	[2]
Impairment of Real Estate	5,000,000		16,400,000																														18,000,000
Servicing Assets and Servicing Liabilities at Fair Value, Assumptions Used to Estimate Fair Value, Discount Rate																																								7.11%									8.09%									1.70%	2.80%	4.00%
Notes Receivable, Fair Value				23,700,000	35,300,000
Trading Securities, Fair Value Disclosure																								22,455,000	21,713,000	22,455,000	21,713,000	0	0	0	0
Notes Payable, Fair Value				1,950,000,000	2,090,000,000
Total																								22,455,000	21,713,000	22,455,000	21,713,000	0	0	0	0
Derivative Liabilities																								(73,000)	(37,000)	0	0	(75,000)	(38,000)	2,000	1,000
Assets, Fair Value Disclosure, Nonrecurring								$ 325,693,000		$ 7,413,000		$ 0		$ 0		$ 320,682,000		$ 0		$ 5,011,000		$ 7,413,000

[1] .

[2] Excludes impairments for properties sold during the year ended December 31, 2011.