Financial Information for Operation Segments (Detail) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Revenues:
Community base rental income	$ 101,468,000	$ 98,336,000	$ 202,244,000	$ 196,433,000
Gross revenue from home sales	4,217,000	1,921,000	6,913,000	3,925,000
Resort base rental income	33,197,000	30,408,000	73,936,000	67,987,000
Brokered resale revenues, net	932,000	482,000	2,727,000	2,225,000
Right-to-use annual payments	12,043,000	12,221,000	23,566,000	23,972,000
Rental home income	3,598,000	2,786,000	6,992,000	5,367,000
Right-to-use contracts current period, gross	3,361,000	2,942,000	6,192,000	5,186,000
Right-to-use contracts current period, deferred	(1,550,000)	(1,285,000)	(2,590,000)	(1,891,000)
Utility and other income	15,787,000	17,097,000	32,470,000	33,053,000
Total revenues	176,753,000	168,383,000	360,528,000	343,324,000
Expenses:
Property operating and maintenance	58,345,000	56,882,000	113,401,000	109,850,000
Cost of home sales	3,919,000	2,514,000	6,700,000	4,681,000
Real estate taxes	11,888,000	11,510,000	24,290,000	23,367,000
Home selling expenses	454,000	399,000	981,000	728,000
Sales and marketing, gross	3,333,000	2,632,000	5,694,000	4,275,000
Rental home operating and maintenance	1,487,000	1,281,000	3,357,000	2,694,000
Sales and marketing, deferred commissions, net	(655,000)	(655,000)	(1,118,000)	(897,000)
Property management	10,170,000	9,312,000	20,303,000	18,947,000
Total expenses	158,741,000	162,930,000	306,651,000	321,140,000
Income from operations	18,012,000	5,453,000	53,877,000	22,184,000
Property Operations Segment [Member]
Revenues:
Community base rental income	101,468,000	98,336,000	202,244,000	196,433,000
Resort base rental income	33,197,000	30,408,000	73,936,000	67,987,000
Right-to-use annual payments	12,043,000	12,221,000	23,566,000	23,972,000
Right-to-use contracts current period, gross	3,361,000	2,942,000	6,192,000	5,186,000
Right-to-use contracts current period, deferred	(1,550,000)	(1,285,000)	(2,590,000)	(1,891,000)
Utility and other income	15,787,000	17,097,000	32,470,000	33,053,000
Ancillary services revenues, net	634,000	151,000	2,112,000	1,566,000
Total revenues	164,940,000	159,870,000	337,930,000	326,306,000
Expenses:
Property operating and maintenance	58,345,000	56,882,000	113,401,000	109,850,000
Real estate taxes	11,888,000	11,510,000	24,290,000	23,367,000
Sales and marketing, gross	3,333,000	2,632,000	5,694,000	4,275,000
Sales and marketing, deferred commissions, net	(655,000)	(655,000)	(1,118,000)	(897,000)
Property management	10,170,000	9,312,000	20,303,000	18,947,000
Total expenses	83,081,000	79,681,000	162,570,000	155,542,000
Income from operations	81,859,000	80,189,000	175,360,000	170,764,000
Home Sales and Rentals Operations segment
Revenues:
Gross revenue from home sales	4,217,000	1,921,000	6,913,000	3,925,000
Brokered resale revenues, net	298,000	331,000	615,000	659,000
Rental home income	3,598,000	2,786,000	6,992,000	5,367,000
Total revenues	8,113,000	5,038,000	14,520,000	9,951,000
Expenses:
Cost of home sales	3,919,000	2,514,000	6,700,000	4,681,000
Home selling expenses	454,000	399,000	981,000	728,000
Rental home operating and maintenance	1,487,000	1,281,000	3,357,000	2,694,000
Total expenses	5,860,000	4,194,000	11,038,000	8,103,000
Income from operations	$ 2,253,000	$ 844,000	$ 3,482,000	$ 1,848,000