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Debt And Lines Of Credit , Narrative - Collateralized Term Loans (Details)	1 Months Ended				3 Months Ended					9 Months Ended		12 Months Ended
	Sep. 30, 2017 USD ($) sites manufactured_home	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($) subsidiary promissory_note RV_community manufactured_home	Jun. 30, 2016 loans subsidiary	Sep. 30, 2017 USD ($) sites manufactured_home	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($) community	Dec. 31, 2016 USD ($) community sites manufactured_home	Sep. 30, 2016 USD ($) RV_community manufactured_home	Sep. 30, 2017 USD ($) sites manufactured_home	Sep. 30, 2016 USD ($) RV_community manufactured_home	Dec. 31, 2016 USD ($) sites manufactured_home
Debt Instrument [Line Items]
Gain (loss) on extinguishment of debt					$ 0	$ 300,000	$ 500,000		$ 0	$ 759,000	$ 0
Reduction in secured borrowing balance								$ 79,100,000		$ 17,674,000	14,718,000
Number of Real Estate Units Released \| community							1	10
Weighted average interest rate	4.60%				4.60%			4.50%		4.60%		4.50%
Number of Units in Real Estate Property \| sites								1,677				1,677
Debt weighted average to maturity, length										8 years 4 months 24 days		8 years 6 months
Total debt	$ 2,822,640,000				$ 2,822,640,000			$ 2,819,567,000		$ 2,822,640,000		$ 2,819,567,000
Repayments of Debt			$ 62,100,000
Repayments of Lines of Credit			$ 300,000,000							$ 675,695,000	$ 441,738,000
Notes Payable to Banks [Member]
Debt Instrument [Line Items]
Debt instrument, face amount								$ 58,500,000.0				$ 58,500,000.0
Interest rate								3.33%				3.33%
Debt instrument term								7 years
Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount		$ 77,000,000.0				$ 77,000,000.0
Interest rate		4.16%				4.16%
Debt instrument term		25 years
Commercial Mortgage Backed Securities [Member]
Debt Instrument [Line Items]
Weighted average interest rate	4.40%				4.40%			5.20%		4.40%		5.20%
Debt weighted average to maturity, length										5 years 9 months 18 days		5 years 7 months 6 days
Total debt	$ 1,032,621,000				$ 1,032,621,000			$ 492,294,000		$ 1,032,621,000		$ 492,294,000
Collateralized Mortgage Backed Securities [Member]
Debt Instrument [Line Items]
Net book value of properties securing collateralized term loans	$ 3,400,000,000				$ 3,400,000,000					$ 3,400,000,000
RV community [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| manufactured_home								7				7
Properties securing debt [Member] \| Collateralized Mortgage Backed Securities [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| sites	76,078				76,078					76,078
Collateralized Term Loan Due August 31, 2017 [Member]
Debt Instrument [Line Items]
Reduction in secured borrowing balance		$ 3,900,000
Debt Instrument, Interest Rate, Stated Percentage		6.54%				6.54%
Collateralized Term Loan Due August 1, 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Defeased							$ 18,900,000
Debt Instrument, Interest Rate, Stated Percentage							6.49%
Collateralized Term Loan Due May 1, 2017 [Member]
Debt Instrument [Line Items]
Reduction in secured borrowing balance							$ 10,000,000
Debt Instrument, Interest Rate, Stated Percentage							5.57%
Operating Partnership [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Interest rate			3.69%						3.69%		3.69%
Amortization term				30 years
Operating Partnership [Member] \| Freddie Mac Financing [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of subsidiaries \| subsidiary			15
Debt instrument, face amount			$ 139,000,000						$ 139,000,000		$ 139,000,000
Amortization term			30 years
Operating Partnership [Member] \| Freddie Mac Financing - Loan 1 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 70,200,000						$ 70,200,000		$ 70,200,000
Number of loans \| promissory_note			5
Interest rate			3.93%						3.93%		3.93%
Debt instrument term			10 years
Operating Partnership [Member] \| Freddie Mac Financing - Loan 2 [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 68,800,000						$ 68,800,000		$ 68,800,000
Number of loans \| promissory_note			10
Interest rate			3.75%						3.75%		3.75%
Debt instrument term			7 years
Operating Partnership [Member] \| Fannie Mae Financing [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of subsidiaries \| subsidiary				17
Debt instrument, face amount			$ 338,000,000						$ 338,000,000		$ 338,000,000
Number of loans \| loans				2
Debt instrument term				10 years
Operating Partnership [Member] \| Fannie Mae Financing [Member] \| Manufactured home community [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| manufactured_home	17				17					17
Operating Partnership [Member] \| Fannie Mae Financing - Term Loan One [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 300,000,000						$ 300,000,000		$ 300,000,000
Interest rate			3.69%						3.69%		3.69%
Operating Partnership [Member] \| Fannie Mae Financing - Term Loan Two [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 38,000,000						$ 38,000,000		$ 38,000,000
Interest rate			3.67%						3.67%		3.67%
Operating Partnership [Member] \| NML Loan Documents [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of subsidiaries \| subsidiary				3
Debt instrument, face amount			$ 405,000,000						$ 405,000,000		$ 405,000,000
Number of loans \| loans				3
Operating Partnership [Member] \| NML Loan Documents - Portfolio A Loan [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of subsidiaries \| subsidiary				2
Debt instrument, face amount			$ 162,000,000						$ 162,000,000		$ 162,000,000
Interest rate			3.53%						3.53%		3.53%
Debt instrument term				10 years
Operating Partnership [Member] \| NML Loan Documents - Portfolio A Loan [Member] \| Manufactured home community [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| manufactured_home			7						7		7
Operating Partnership [Member] \| NML Loan Documents - Portfolio A Loan [Member] \| RV community [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| RV_community			1						1		1
Operating Partnership [Member] \| NML Loan Documents - Portfolio B Loan [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of subsidiaries \| subsidiary				1
Debt instrument, face amount			$ 163,000,000						$ 163,000,000		$ 163,000,000
Interest rate			3.71%						3.71%		3.71%
Debt instrument term				12 years
Operating Partnership [Member] \| NML Loan Documents - Portfolio B Loan [Member] \| Manufactured home community [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| manufactured_home			8						8		8
Operating Partnership [Member] \| NML Loan Documents - Portfolio C Loan [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount			$ 80,000,000						$ 80,000,000		$ 80,000,000
Interest rate			3.71%						3.71%		3.71%
Debt instrument term				12 years
Operating Partnership [Member] \| NML Loan Documents - Portfolio C Loan [Member] \| RV community [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| manufactured_home			1						1		1
Ocean West [Member]
Debt Instrument [Line Items]
Number of Units in Real Estate Property \| sites	130				130					130
Ocean West [Member] \| Secured Debt [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 4,600,000.0				$ 4,600,000.0					$ 4,600,000.0
Interest rate	4.34%				4.34%					4.34%
Debt instrument term	9 years 9 months 18 days