Borrowing Arrangements - Additional Information (Detail) (USD $)	3 Months Ended		9 Months Ended			9 Months Ended	1 Months Ended			1 Months Ended		1 Months Ended	9 Months Ended			0 Months Ended	9 Months Ended
	Sep. 30, 2013 integer Rate	Sep. 30, 2012	Sep. 30, 2013 Rate integer	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Old Credit Facilities [Member]	Jul. 31, 2012 Amended Line of Credit Facility	Sep. 30, 2013 New Credit Facilities [Member]	Sep. 30, 2013 Minimum	Jul. 31, 2012 Minimum Amended Line of Credit Facility Rate	Sep. 30, 2013 Maximum	Jul. 31, 2012 Maximum Amended Line of Credit Facility Rate	Sep. 30, 2013 Term Loans	Sep. 30, 2013 Term Loans Minimum Rate	Sep. 30, 2013 Term Loans Maximum Rate	Jul. 30, 2013 Manufactured Home [Member] Old Credit Facilities [Member]	Sep. 30, 2013 Manufactured Home [Member] Old Credit Facilities [Member]	Jul. 18, 2013 Manufactured Home [Member] Old Credit Facilities [Member]	Sep. 30, 2013 Manufactured Home [Member] Minimum Old Credit Facilities [Member]	Sep. 30, 2013 Manufactured Home [Member] Maximum Old Credit Facilities [Member]	Sep. 30, 2013 Segment, Discontinued Operations [Member]	Dec. 31, 2012 Segment, Discontinued Operations [Member]
Debt Instrument [Line Items]
Unsecured Debt	$ 200,000,000		$ 200,000,000		$ 200,000,000
Debt Instrument, Maturity Date													Jun. 30, 2017
Mortgage notes payable	1,994,308,000		1,994,308,000		2,061,610,000			347,100,000														8,300,000
Debt Instrument, Unamortized Premium																					400,000
Debt, Weighted Average Interest Rate	5.10%		5.10%
Debt, minimum interest rate			3.90%
Debt, maximum interest rate			8.90%
Debt, maturity year									2014		2038							2020	2014	2015
Extinguishment of Debt, Amount	36,530,000	0	37,911,000	0
Number of pledge properties	152		152		170	9											29	1
Carrying values of properties encumbered	2,390,000,000		2,390,000,000		2,485,000,000
Repayments of Long-term Debt						73,700,000										7,900,000	312,200,000
Debt Instrument, Interest Rate, Stated Percentage						6.00%		4.50%									5.70%	7.20%
Debt instrument, interest rate based on margin over LIBOR										1.40%		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%
Derivative, Maturity Years													3 years
Lines of credit, borrowing capacity	380,000,000		380,000,000		380,000,000
Proceeds from Lines of Credit			20,000,000	0
Lines of credit, maturity date							Sep. 15, 2016
Line of credit facility, interest rate based on margin over LIBOR			Our amended LOC bears a LIBOR rate plus a maximum of 1.40% to 2.00%, contains a 0.25% to 0.40% facility rate and has a maturity date of September 15, 2016. We have a one year extension option under our LOC.
Repayments of Lines of Credit			20,000,000	0
Lines of credit, extension option							1 year
Line of Credit Facility, Commitment Fee Amount		$ 1,300,000
Line of credit, facility rate										0.25%		0.40%