Segment Information (Details 2) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Information
Rental income		$ 707,380	$ 709,390	$ 601,632
Tenant reimbursements and other income		178,156	172,515	139,712
Operating expenses		(370,869)	(356,604)	(297,408)
NOI		514,667	525,301	443,936
Reconciliation of NOI to net income
NOI		514,667	525,301	443,936
Depreciation and amortization		(218,854)	(209,759)	(171,662)
General and administrative		(77,209)	(46,057)	(38,221)
Loss on asset impairment				(3,036)
Acquisition related costs		(318)	(5,648)	(9,731)
Operating income		218,286	263,837	221,286
Interest and other income		1,229	1,404	1,662
Interest expense		(173,011)	(201,840)	(191,876)
Loss on early extinguishment of debt	(60,027)	(60,052)	(287)	(35)
Gain on sale of equity investment		66,293
Gain on issuance of shares by an equity investee			7,246	11,177
Income from continuing operations before income tax expense and equity in earnings of investees		52,745	70,360	42,214
Income tax expense		(2,634)	(3,207)	(1,347)
Equity in earnings of investees		25,754	11,420	11,377
Income from continuing operations		75,865	78,573	52,244
Income from discontinued operations		15,867	9,783	22,307
Loss on asset impairment from discontinued operations		(227,122)	(168,632)	(7,319)
Loss on early extinguishment of debt from discontinued operations		(1,011)	(1,608)
Net gain on sale of properties from discontinued operations		(22,162)	2,039	42,752
(Loss) income before gain on sale of properties		(158,563)	(79,845)	109,984
Gain on sale of properties		1,596
Net (loss) income		$ (156,967)	$ (79,845)	$ 109,984