Borrowing Arrangements - Additional Information (Detail)	3 Months Ended		12 Months Ended	15 Months Ended
	Mar. 31, 2016 USD ($) Property loan Rate	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) Property	Mar. 31, 2016 USD ($) Property Rate
Debt Instrument [Line Items]
Deferred financing costs, net	$ 19,000,000		$ 19,700,000	$ 19,000,000
Mortgage notes payable	$ 1,907,074,000		$ 1,926,880,000	$ 1,907,074,000
Weighted average interest rate | Rate	4.90%			4.90%
Stated interest rate	5.48%			5.48%
Number of pledged properties | Property	126		127	126
Pledged assets, not separately reported	$ 2,200,000,000		$ 2,200,000,000	$ 2,200,000,000
New mortgage notes payable financing proceeds	0	$ 395,323,000
Unsecured debt	199,224,000		$ 199,172,000	199,224,000
Maximum borrowing capacity	400,000,000			400,000,000
Additional borrowing capacity	$ 100,000,000			$ 100,000,000
Debt instrument, term (in years)		1 year
Old Credit Facilities
Debt Instrument [Line Items]
Number of maturing mortgage loans repaid | loan	1
Debt repaid	$ 9,800,000
Minimum
Debt Instrument [Line Items]
Interest rate during period (in percentage) | Rate	1.20%
Line of credit facility, annual fees (in percentage)	0.20%
Maximum
Debt Instrument [Line Items]
Interest rate during period (in percentage) | Rate	1.65%
Line of credit facility, annual fees (in percentage)	0.35%
Secured Debt [Member] | Minimum
Debt Instrument [Line Items]
Stated interest rate	3.45%			3.45%
Secured Debt [Member] | Maximum
Debt Instrument [Line Items]
Stated interest rate	8.87%			8.87%
Line of Credit [Member] | Old Credit Facilities
Debt Instrument [Line Items]
Weighted average interest rate			5.58%
Loss on extinguishment of debt			$ 17,000,000
Debt repaid				$ 370,200,000
Line of Credit [Member] | New Credit Facilities [Member]
Debt Instrument [Line Items]
Weighted average interest rate			3.93%
Debt instrument maturity year			21 years
Number of pledged properties | Property			26
New mortgage notes payable financing proceeds			$ 395,300,000
Term Loans
Debt Instrument [Line Items]
Unsecured debt	$ 200,000,000			200,000,000
Maturity date	Jan. 10, 2020
Term Loans | Minimum
Debt Instrument [Line Items]
Variable rate in addition to LIBOR rate (in percentage) | Rate	1.35%
Term Loans | Maximum
Debt Instrument [Line Items]
Variable rate in addition to LIBOR rate (in percentage) | Rate	1.95%
Manufactured homes
Debt Instrument [Line Items]
Number of pledged properties towards loans repaid | Property	1
Adjustments for New Accounting Pronouncement | Mortgages Notes Payable
Debt Instrument [Line Items]
Deferred financing costs, net	$ 18,200,000		18,900,000	18,200,000
Adjustments for New Accounting Pronouncement | Term Loan
Debt Instrument [Line Items]
Deferred financing costs, net	800,000		800,000	800,000
Adjustments for New Accounting Pronouncement | Escrow Deposits, Goodwill and other Assets
Debt Instrument [Line Items]
Deferred financing costs, net	$ 3,400,000		$ 3,700,000	$ 3,400,000