Summary of Significant Accounting Policies - Additional Information (Detail)	6 Months Ended	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) Property State Segment	Dec. 31, 2016 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments | Segment		1
Impairment loss on real estate assets	$ 0	$ 0	$ 0
Impairment loss	0	0	0
Restricted cash	92,475,000	175,665,000	87,616,000
Prepaid rental income		2,700,000	2,900,000
Unrealized loss on interest rate cap	2,933,000	$ 701,000	1,378,000
Number of wholly owned properties acquired | Property		230
Number of states in properties located | State		49
Interest Rate Cap [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest rate caps purchased		$ 5,000,000
Derivative, term of contract		4 years
Notional amount		$ 1,261,000,000
Derivative strike rate		3.50%
Unrealized loss on interest rate cap	$ 2,900,000	$ 700,000	1,400,000
Derivative assets, fair value			700,000
Maximum [Member] | Interest Rate Cap [Member]
Summary Of Significant Accounting Policies [Line Items]
Derivative assets, fair value		$ 100,000
Master Lease [Member]
Summary Of Significant Accounting Policies [Line Items]
Right to recapture property space		50.00%
Sears Holdings Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Right to recapture property space		100.00%
Sears Holdings Corporation [Member] | Master Lease [Member]
Summary Of Significant Accounting Policies [Line Items]
Right to recapture property space		100.00%
Restricted Cash Reserves [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		$ 151,300,000	65,500,000
Basic Property Carrying Costs [Member]
Summary Of Significant Accounting Policies [Line Items]
Restricted cash		$ 21,700,000	$ 19,200,000
Operating Partnership [Member] | ESL [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of operating partnership interest held by parent		63.80%