Real Estate - Summary of Dispositions (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2013	Jun. 30, 2014 sqft	Jun. 30, 2014 Continuing Operations [Member] Contributions to co-investment ventures [Member] sqft Property	Jun. 30, 2013 Continuing Operations [Member] Contributions to co-investment ventures [Member] sqft Property	Jun. 30, 2014 Continuing Operations [Member] Dispositions to third parties [Member] sqft Property	Jun. 30, 2013 Continuing Operations [Member] Dispositions to third parties [Member]	Jun. 30, 2013 Discontinued Operations [Member] Property sqft
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties				110	210	65		20
Square feet			12,600,000	20,416,000	59,911,000	8,808,000		1,888,000
Net proceeds				$ 1,203,815	$ 5,047,745	$ 576,004	$ 60,915	$ 162,703
Net gains on contributions and dispositions				59,160	393,626	127,478	6,254
Net gains on dispositions, including taxes	$ 13,467	$ 19,301						$ 19,301