Schedule III - Real Estate Assets and Accumulated Depreciation Activity (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Reconciliation of Carrying Amount of Real Estate Investments and Accumulated Depreciation [Roll Forward]
Balance, end of period	$ 8,301,013	$ 7,767,819	$ 8,611,331
Additions and improvements	282,664	217,161	201,359
Acquisitions of real estate assets	29,912	474,623	11,197
Disposals, deconsolidations and accumulated depreciation on impairments	(412,976)	(108,554)	(999,685)
Transfers from real estate assets	(8,031)	808	(476)
Impairment of real estate assets	(69,068)	(50,844)	(55,907)
Balance, end of period	8,123,514	8,301,013	7,767,819
Accumulated depreciation, beginning of period	1,972,031	1,762,149	1,721,194
Depreciation expense	253,142	247,702	260,847
Accumulated depreciation on real estate assets sold, retired, or deconsolidated	(168,816)	(37,820)	(219,892)
Accumulated depreciation, end of period	$ 2,056,357	$ 1,972,031	$ 1,762,149