Segment Financial Information (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	$ 176,609,000	$ 157,322,000	$ 524,654,000	$ 416,256,000
Operations expenses	(88,367,000)	(81,083,000)	(256,867,000)	(213,933,000)
Income from segment operations	88,242,000	76,239,000	267,787,000	202,323,000
Interest income	2,454,000	2,188,000	7,253,000	4,173,000
Depreciation on real estate and rental homes	(26,294,000)	(22,925,000)	(78,620,000)	(59,234,000)
Amortization of in-place leases	(7,548,000)	(10,759,000)	(44,314,000)	(10,759,000)
Income from operations	56,854,000	44,743,000	152,106,000	136,503,000
Reconciliation to Consolidated net income
Other revenues	2,765,000	4,534,000	6,039,000	6,448,000
General and administrative	(6,535,000)	(6,412,000)	(19,724,000)	(18,070,000)
Acquisition Costs	0	(15,216,000)	0	(17,333,000)
Interest and related amortization	(31,640,000)	(26,084,000)	(93,434,000)	(68,931,000)
Rent control initiatives and other	(221,000)	(467,000)	(1,067,000)	(1,558,000)
Equity in income of unconsolidated joint ventures	269,000	257,000	1,524,000	1,582,000
Consolidated net income	21,492,000	1,355,000	45,444,000	38,641,000
Total assets	3,497,125,000	3,292,805,000	3,497,125,000	3,292,805,000	3,496,101,000
Capital improvements			53,164,000	41,396,000
Property Operations segment
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	170,776,000	153,234,000	507,739,000	406,105,000
Operations expenses	(83,973,000)	(77,758,000)	(243,773,000)	(205,590,000)
Income from segment operations	86,803,000	75,476,000	263,966,000	200,515,000
Interest income	750,000	919,000	2,387,000	2,500,000
Depreciation on real estate and rental homes	(24,703,000)	(21,675,000)	(74,101,000)	(56,158,000)
Amortization of in-place leases	(7,396,000)	(10,759,000)	(43,220,000)	(10,759,000)
Income from operations	55,454,000	43,961,000	149,032,000	136,098,000
Reconciliation to Consolidated net income
Total assets	3,260,654,000	3,091,731,000	3,260,654,000	3,091,731,000
Capital improvements			21,459,000	16,728,000
Home Sales and Rentals Operations segment
Segment Reporting Information [Line Items]
Segment Reporting Information, Revenue for Reportable Segment	5,833,000	4,088,000	16,915,000	10,151,000
Operations expenses	(4,394,000)	(3,325,000)	(13,094,000)	(8,343,000)
Income from segment operations	1,439,000	763,000	3,821,000	1,808,000
Interest income	1,704,000	1,269,000	4,866,000	1,673,000
Depreciation on real estate and rental homes	(1,591,000)	(1,250,000)	(4,519,000)	(3,076,000)
Amortization of in-place leases	(152,000)	0	(1,094,000)	0
Income from operations	1,400,000	782,000	3,074,000	405,000
Reconciliation to Consolidated net income
Total assets	236,471,000	201,074,000	236,471,000	201,074,000
Capital improvements			$ 31,705,000	$ 24,668,000