Real Estate - Summary of Dispositions (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 sqft Property	Mar. 31, 2013 Property sqft
Continuing Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties	5	209
Square feet	715,000	58,888,000
Net proceeds from contributions and dispositions	$ 81,231	$ 4,876,214
Net gains from contributions and dispositions	17,055	338,845
Discontinued Operations [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Number of properties		7
Square feet		432,000
Net proceeds from contributions and dispositions		35,546
Net gains from contributions and dispositions		$ 5,834