Other Assets and Other Liabilities (Details) (USD $)	3 Months Ended			6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011	Jun. 30, 2012		Jun. 30, 2011	Dec. 31, 2011
Deferred expenses and other assets, net
Other receivables	$ 19,639,000			$ 19,639,000			$ 13,943,000
Deferred financing fees, net	17,573,000	[1]		17,573,000	[1]		21,443,000	[1]
Net lease in-place lease intangibles, net	14,363,000	[2]		14,363,000	[2]		17,013,000	[2]
Leasing costs, net	12,994,000	[3]		12,994,000	[3]		12,423,000	[3]
Derivative asset	8,660,000			8,660,000			0
Corporate furniture, fixtures and equipment, net	8,086,000	[4]		8,086,000	[4]		9,034,000	[4]
Prepaid expenses	5,380,000			5,380,000			5,441,000
Other assets	18,605,000			18,605,000			28,555,000
Deferred expenses and other assets, net	105,300,000			105,300,000			107,852,000
Accumulated amortization of deferred financing fees	19,400,000			19,400,000			13,300,000
Accumulated amortization on net lease intangibles	34,000,000			34,000,000			33,400,000
Amortization expense related to net lease intangibles	1,000,000		1,700,000	2,300,000		3,400,000
Accumulated amortization on leasing costs	5,000,000			5,000,000			5,500,000
Accumulated depreciation on corporate furniture, fixtures and equipment	7,700,000			7,700,000			8,100,000
Accounts payable, accrued expenses and other liabilities
Accrued interest payable	38,030,000			38,030,000			30,122,000
Accrued expenses	29,104,000			29,104,000			36,332,000
Security deposits and other investment deposits	12,463,000			12,463,000			12,192,000
Unearned operating lease income	8,917,000			8,917,000			10,073,000
Property taxes payable	8,274,000			8,274,000			6,495,000
Other liabilities	14,706,000			14,706,000			11,479,000
Accounts payable, accrued expenses and other liabilities	111,494,000			111,494,000			106,693,000
Taxable REIT Subsidiaries (TRSs)
Deferred Tax Asset
Deferred tax assets	57,657,000	[5]		57,657,000	[5]		50,889,000	[5]
Valuation allowance	(57,657,000)			(57,657,000)			(50,889,000)
Deferred tax assets, net	0			0			0
Real estate asset basis differences	34,200,000			34,200,000			28,700,000
Net operating loss carryforwards	22,500,000			22,500,000			22,800,000
Investment basis differences	$ 1,000,000			$ 1,000,000			$ (600,000)

[1] Accumulated amortization on deferred financing fees was $19.4 million and $13.3 million as of June 30, 2012 and December 31, 2011, respectively.

[2] Represents unamortized finite lived intangible assets related to the prior acquisition of net lease assets. Accumulated amortization on net lease intangibles was $34.0 million and $33.4 million as of June 30, 2012 and December 31, 2011, respectively. Amortization expense related to these assets was $1.0 million and $1.7 million for the three months ended June 30, 2012 and 2011, respectively

[3] Accumulated amortization on leasing costs was $5.0 million and $5.5 million as of June 30, 2012 and December 31, 2011, respectively.

[4] Accumulated depreciation on corporate furniture, fixtures and equipment was $7.7 million and $8.1 million as of June 30, 2012 and December 31, 2011, respectively.

[5] Deferred tax assets as of June 30, 2012 primarily include real estate basis differences of $34.2 million, net operating loss carryforwards of $22.5 million and investment basis differences of $1.0 million. Deferred tax assets as of December 31, 2011 include real estate basis differences of $28.7 million, net operating loss carryforwards of $22.8 million, and investment basis differences of $(0.6) million.