Schedule III - Real Estate and Accumulated Depreciation (Reconciliation of Real Estate and Accumulated Depreciation) (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 [Roll Forward]
Balance at the Beginning of the Year	$ 4,726,169	$ 4,793,080	$ 4,834,111
Additions:
Acquisitions	347,510	50,579	31,454
Capital Expenditures	109,740	90,619	133,550
Less:
Dispositions	(474,275)	(168,408)	(163,971)
Balance at the End of the Year	4,669,289	4,726,169	4,793,080
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at the beginning of the year	954,665	865,710	776,078
Real Estate Accumulated Depreciation Additions [Abstract]
Depreciation expense — continuing operations	150,236	154,095	157,691
Depreciation expense — discontinued operations	9,164	2,143	1,185
SEC Schedule III, Real Estate, Other Deductions	(39,855)	(39,701)	(42,064)
Real Estate Accumulated Depreciation Less Dispositions [Abstract]
Dispositions	(91,890)	(28,270)	(62,022)
SEC Schedule III, Real Estate Accumulated Depreciation, Other Deductions	(38,367)	(39,013)	(7,222)
Balance at the end of the year	$ 983,808	$ 954,665	$ 865,710