Borrowing Arrangements - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended		12 Months Ended	3 Months Ended		1 Months Ended	6 Months Ended		1 Months Ended	6 Months Ended		1 Months Ended	6 Months Ended
	Sep. 30, 2011	Jun. 30, 2012 Property	Jun. 30, 2011	Dec. 31, 2011 Property	Jun. 30, 2012 New Credit Facilities RV resort Property	Jun. 30, 2012 Old Credit Facilities RV resort	Jul. 31, 2012 Amended Line of Credit Facility	Jun. 30, 2012 Minimum	Dec. 31, 2011 Minimum	Jul. 31, 2012 Minimum Amended Line of Credit Facility	Jun. 30, 2012 Maximum	Dec. 31, 2011 Maximum	Jul. 31, 2012 Maximum Amended Line of Credit Facility	Jun. 30, 2012 Term Loans	Jun. 30, 2012 Term Loans Minimum	Jun. 30, 2012 Term Loans Maximum
Debt Instrument [Line Items]
Mortgage notes payable		$ 2,088,450,000		$ 2,084,683,000
Mortgage notes payable, weighted average interest rate		5.50%			5.10%	5.40%
Debt, minimum interest rate		4.70%		4.65%
Debt, maximum interest rate		8.90%		8.87%
Debt, maturity year					2022			2012	2012		2023	2023
Number of pledge properties		174		174	2
Carrying values of properties encumbered		2,585,000,000		2,578,000,000
New mortgage notes payable financing proceeds	200,000,000	85,500,000			85,500,000
Principal payments and mortgage debt payoff		78,297,000	56,281,000			63,300,000
Debt, maturity date						Jun. 01, 2014								Jun. 30, 2017
Debt instrument face amount														200,000,000
Debt, extension option period														1 year
Debt instrument, interest rate based on margin over LIBOR								1.65%		1.40%	2.50%		2.00%		1.85%	2.80%
Start date to repay debt without penalty on prepayment														Jul. 01, 2014
Debt, percentage of prepayment penalty														2.00%
LIBOR Swap Agreement, period														3 years
Lines of credit, borrowing capacity		$ 380,000,000		$ 380,000,000
Lines of credit, maturity date		Sep. 18, 2015					Sep. 15, 2016
Line of credit facility, interest rate based on margin over LIBOR		The Company’s LOC with a maximum borrowing capacity of $380 million bore interest at a LIBOR rate plus 1.65% to 2.50%
Line of credit, facility fee								0.30%			0.40%
Lines of credit, extension option							1 year
Line of credit, facility rate										0.25%			0.40%