Consolidated Variable Interest Entities, Schedule of Variable Interest Entities (Details)	1 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2018 USD ($)	Sep. 30, 2018 USD ($) site sites properties Rate	Dec. 31, 2017 USD ($) site Rate
Variable Interest Entity [Line Items]
Investment property, net		$ 6,053,977,000	$ 5,645,354,000
Other assets, net (including $20,655 and $1,659 for consolidated variable interest entities at September 30, 2018 and December 31, 2017; see Note 8)		165,237,000	134,304,000
Mortgage loans payable (including $44,426 and $41,970 for consolidated variable interest entities at September 30, 2018 and December 31, 2017; see Note 8)		2,819,225,000	2,867,356,000
Other liabilities (including $7,434 and $1,468 for consolidated variable interest entities at September 30, 2018 and December 31, 2017; see Note 8)		163,459,000	138,536,000
Liabilities		3,367,285,000	3,405,204,000
Consolidated variable interest entities		$ 7,544,000	$ 4,285,000
VIE as a Percentage of Consolidated Assets | Rate		4.80%	0.80%
VIE as a Percentage of Consolidated Liabilities | Rate		2.60%	1.20%
VIE as a Percentage of Total Equity		1.00%
Sites | site		4,506	2,667
Cash		$ 280,175,000	$ 116,218,000
Variable Interest Entity, Primary Beneficiary [Member]
Variable Interest Entity [Line Items]
Investment property, net		300,693,000	50,193,000
Other assets, net (including $20,655 and $1,659 for consolidated variable interest entities at September 30, 2018 and December 31, 2017; see Note 8)		20,655,000	1,659,000
Total Assets		321,348,000	51,852,000
Mortgage loans payable (including $44,426 and $41,970 for consolidated variable interest entities at September 30, 2018 and December 31, 2017; see Note 8)		44,426,000	41,970,000
Preferred OP units - mandatorily redeemable		35,277,000	0
Other liabilities (including $7,434 and $1,468 for consolidated variable interest entities at September 30, 2018 and December 31, 2017; see Note 8)		7,434,000	1,468,000
Liabilities		87,137,000	43,438,000
Equity Interests		21,976,000	0
Consolidated variable interest entities		7,544,000	4,285,000
Total Liabilities and Stockholder's Equity		116,657,000	47,723,000
Preferred Equity, Mandatorily Redeemable [Member]
Variable Interest Entity [Line Items]
Preferred OP units - mandatorily redeemable		35,277,000	$ 0
Northgate Additional Consideration [Member]
Variable Interest Entity [Line Items]
Cash		$ 0
Northgate [Member]
Variable Interest Entity [Line Items]
Number of Real Estate Properties | properties		10
Sites | sites		2,700
Northgate [Member] | Sun NG RV Resorts [Member]
Variable Interest Entity [Line Items]
Ownership percentage		80.00%
Payments to Acquire Interest in Joint Venture	$ 61.6
Northgate [Member] | NG Sun LLC [Member]
Variable Interest Entity [Line Items]
Ownership percentage		20.00%
Payments to Acquire Interest in Joint Venture	$ 15.4
Development Sites [Member] | Northgate [Member]
Variable Interest Entity [Line Items]
Sites | sites		940
Ground Up Development [Member] | Northgate [Member]
Variable Interest Entity [Line Items]
Number of Real Estate Properties | properties		1
Preferred Partner [Member] | Northgate Additional Consideration [Member]
Variable Interest Entity [Line Items]
Cash		$ 0
Bridge Loan [Member] | Northgate Additional Consideration [Member]
Variable Interest Entity [Line Items]
Cash		$ 0