Investment in Real Estate - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended						6 Months Ended	3 Months Ended				6 Months Ended											3 Months Ended		6 Months Ended
	Jul. 31, 2013	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	May 08, 2013	Apr. 02, 2013	Dec. 31, 2012	Mar. 31, 2012	Jun. 30, 2013 Purchase Price Allocation Adjustments	Sep. 30, 2013 Subsequent Event [Member]	Aug. 01, 2013 Subsequent Event [Member]	Jul. 19, 2013 Subsequent Event [Member]	Jul. 02, 2013 Subsequent Event [Member]	Jun. 30, 2013 Rochester Hills, MI [Member] Avon On The Lake [Member]	Jun. 30, 2013 White Lake, MI [Member] Cranberry Lake [Member]	Jun. 30, 2013 Chesterfield, MI [Member] Fairchild Lake [Member]	Jun. 30, 2013 Wyoming, MI [Member] Ferrand Estates [Member]	Jun. 30, 2013 Grand Blanc, MI [Member] Grand Blanc [Member]	Jun. 30, 2013 Holly, MI [Member] Holly Hills [Member]	Jun. 30, 2013 Novi, MI [Member] Oakland Glens [Member]	Jun. 30, 2013 Davison, MI [Member] Old Orchard [Member]	Jun. 30, 2013 Kalamazoo, MI [Member] Royal Estates [Member]	Jun. 30, 2013 Macomb, MI [Member] Westbrook [Member]	Jun. 30, 2013 Macomb, MI [Member] Westbridge Manor [Member]	Jun. 30, 2013 Segment, Discontinued Operations [Member]	Jun. 30, 2012 Segment, Discontinued Operations [Member]	Jun. 30, 2013 Segment, Discontinued Operations [Member]	Jun. 30, 2012 Segment, Discontinued Operations [Member]	Dec. 31, 2012 Segment, Discontinued Operations [Member]
Real Estate Properties [Line Items]
Depreciation Expense Adjustment				$ 3,400,000
Asset acquisition price adjustments period										1 year
Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax		0	0	958,000	0
Number of manufactured home communities acquired	3
Number Of Acquired Sites												1,207
Business Acquisition, Cost of Acquired Entity, Purchase Price												102,000,000
Employee's financial interest upon the closing of the Acquisition													3,400,000
Ground Lease Escrow Shares		197,668		197,668					227,586
Escrow Share Distribution							29,918							30,268
Fair Value of Escrow Fund		6,700,000		6,700,000
Number Of Properties Disposed				11
Number of Sites Disposed				5,344											616	328	344	419	478	241	724	200	183	387	1,424
Purchase Price For Disposed Properties						165,000,000
Gain (Loss) on Disposition of Real Estate, Discontinued Operations											41,000,000
Land		984,224,000		984,224,000				984,224,000																		28,611,000		28,611,000		28,611,000
Buildings and Improvements, Gross		515,801,000		515,801,000				495,127,000																		101,048,000		101,048,000		98,255,000
Real Estate Investment Property, Accumulated Depreciation		1,004,300,000		1,004,300,000				948,581,000																		(16,609,000)		(16,609,000)		(15,077,000)
Other Assets		55,105,000		55,105,000				45,214,000																		6,999,000		6,999,000		8,063,000
Assets of Disposal Group, Including Discontinued Operation		120,049,000	118,252,000	120,049,000	118,252,000			119,852,000
Secured Debt		2,122,883,000		2,122,883,000				2,061,610,000																		8,163,000		8,163,000		8,256,000
Other Liabilities																										2,652,000		2,652,000		1,802,000
Liabilities of Disposal Group, Including Discontinued Operation		10,815,000		10,815,000				10,058,000																		10,815,000		10,815,000		10,058,000
Debt Instrument, Unamortized Premium																										400,000		400,000
Community Base Rental Income		101,468,000	98,336,000	202,244,000	196,433,000																					5,080,000	4,861,000	10,117,000	9,718,000
Rental Home Income		3,598,000	2,786,000	6,992,000	5,367,000																					849,000	572,000	1,620,000	1,034,000
Utility And Other Income		15,787,000	17,097,000	32,470,000	33,053,000																					515,000	485,000	997,000	932,000
Disposal Group, Including Discontinued Operation, Revenue																										6,444,000	5,918,000	12,734,000	11,684,000
Disposal Group, Including Discontinued Operation, Operating Expense																										2,473,000	2,148,000	4,923,000	4,479,000
Disposal Group, Including Discontinued Operation, Operating Income (Loss)																										3,971,000	3,770,000	7,811,000	7,205,000
Gains (Losses) on Sales of Other Real Estate																										(40,000)	(46,000)	(75,000)	(40,000)
Disposal Group Including Discontinued Operation Other Income and Expenses																										(635,000)	(3,238,000)	(1,243,000)	(6,386,000)
Interest Expense, Debt		30,377,000	30,705,000	60,500,000	61,528,000																					(131,000)	(133,000)	(260,000)	(266,000)
Income (Loss) from Discontinued Operations, Net of Tax, Including Portion Attributable to Noncontrolling Interest		$ 3,165,000	$ 353,000	$ 7,191,000	$ 513,000																					$ 3,165,000	$ 353,000	$ 6,233,000	$ 513,000