Reconciliation of Net Income Attributable to Common Stockholders to Taxable Net Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Schedule of Components of Income Before Income Tax Expense (Benefit) [Line Items]
Net income attributable to common stockholders	$ 323,085	[1]	$ 44,824	[1]	$ 43,373	[1]	$ 30,341	[1]	$ 27,030	[1]	$ 24,654	[1]	$ 51,125	[1]	$ 72,523	[1]	$ 441,622	$ 175,331	$ 155,647
GAAP gain on sale of communities (in excess of) less than tax gain																	(84,152)	3,812	21,915
Depreciation/amortization timing differences on real estate																	8,536	8,266	2,866
Tax compensation expense less than (in excess of) GAAP																	(55,972)	(12,202)	12,626
Impairment loss																	14,052		19,088
Other adjustments																	2,486	12,628	12,761
Taxable net income																	$ 326,572	$ 187,835	$ 224,903

[1] Amounts may not equal full year results due to rounding.