Combined Results of Operations of Properties Held for Sale or Disposed (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental income	$ 3,300,000	$ 2,500,000	$ 1,900,000
Utility and other income	64,432,000	53,843,000	48,357,000
Property operating expenses	(226,952,000)	(200,623,000)	(185,786,000)
Income from operations	213,628,000	177,858,000	172,032,000
Income from home sales operations	8,566,000	6,088,000	6,120,000
Interest and related amortization	(124,524,000)	(99,668,000)	(91,151,000)
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax	$ 4,596,000	$ 0	$ (231,000)