Assets Held for Sale and Discontinued Operations - Income Attributable to Discontinued Operations (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets Held For Sale [Line Items]
Rental income and recoveries	$ 82,719	$ 141,547	$ 225,064
Rental expenses	(26,665)	(38,657)	(64,577)
Depreciation and amortization	(27,478)	(51,035)	(64,027)
Interest expense	(944)	(1,217)
Income attributable to disposed properties and assets held for sale	27,632	50,638	96,460
Net gains on dispositions	65,927	64,489	326,004
Impairment charges	(30,596)	(2,659)	(87,702)
Income tax on dispositions	(233)	(3,216)	(3,728)
Total discontinued operations	$ 62,730	$ 109,252	$ 331,034