Segment Information - Schedule of Reconciliation of NOI to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Segment Reporting [Abstract]
Rental income	$ 125,459	$ 174,216	$ 457,128	$ 518,663
Tenant reimbursements and other income	33,749	42,379	118,829	130,386
Operating expenses	(73,571)	(99,392)	(261,128)	(293,824)
NOI	85,637	117,203	314,829	355,225
Depreciation and amortization	(40,522)	(57,213)	(156,858)	(168,693)
General and administrative	(16,249)	(47,450)	(43,718)	(96,395)
Loss on asset impairment	0	0	(17,162)	(17,922)
Acquisition related costs	0	0	0	(5)
Operating income	28,866	12,540	97,091	72,210
Interest and other income	637	406	4,813	1,071
Interest expense	(25,111)	(35,245)	(82,926)	(111,079)
(Loss) gain on early extinguishment of debt	(3,887)	6,699	6,111	6,699
Gain on sale of equity investment	0	171,754	0	171,721
Gain on issuance of shares by an equity investee	0	0	0	17,020
Foreign currency exchange loss	(9,809)	0	(8,953)	0
Gain on sale of properties	39,793	0	42,953	0
Income from continuing operations before income taxes and equity in earnings of investees	30,489	156,154	59,089	157,642
Income tax expense	(23)	(703)	(2,377)	(2,166)
Equity in earnings of investees	0	1,072	0	24,460
Income from continuing operations	30,466	156,523	56,712	179,936
Income from discontinued operations	0	95	0	8,220
Gain (loss) on asset impairment from discontinued operations	0	122	0	(2,238)
Loss on early extinguishment of debt from discontinued operations	0	0	0	(3,345)
Net income	$ 30,466	$ 156,740	$ 56,712	$ 182,573