Real Estate - Summary of Dispositions (Detail) ft² in Thousands, $ in Thousands		12 Months Ended
		Dec. 31, 2015 USD ($) ft² Property	Dec. 31, 2014 USD ($) ft² Property	Dec. 31, 2013 USD ($) ft² Property
Continuing Operations [Member] | Contributions to unconsolidated co-investment ventures [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | Property		31	126	254
Square feet | ft²		8,355	25,247	71,503
Net proceeds		$ 835,385	$ 1,825,311	$ 6,479,707
Net gains on contributions		$ 148,987	$ 188,268	555,196
Continuing Operations [Member] | Dispositions to Third Parties [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | Property		136	145
Square feet | ft²		23,024	19,856
Net proceeds		$ 2,352,645	$ 1,365,318	177,273
Net gains on contributions		$ 609,900	$ 336,203	$ 7,673
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of buildings | Property				89
Square feet | ft²				9,196
Net proceeds				$ 608,286
Net gains on dispositions, including related impairment charges and taxes	[1]			$ 116,550

[1] We recorded $1.2 million of income tax expense in 2013 related to the disposition of properties in discontinued operations.