Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended		6 Months Ended
	Jun. 11, 2015 JointVenture	Jun. 30, 2019 USD ($) Property State	Jun. 30, 2018 USD ($) shares	Jun. 30, 2019 USD ($) Property JointVenture State Segment Parcel	Jun. 30, 2018 USD ($) shares	Mar. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 29, 2018 shares	Mar. 31, 2018 shares	Dec. 31, 2017 shares
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments | Segment				1
Impairment loss on real estate assets		$ 0	$ 0	$ 0	$ 0
Gain on sale of real estate				32,873,000	76,018,000
Real estate held for sale, assets		5,277,000		5,277,000				$ 3,094,000
Real estate held for sale, liabilities		0		0				0
Impairment loss		0	0	0	0
Restricted cash		$ 0	$ 166,458,000	$ 0	$ 166,458,000			0
Revenue performance obligation satisfied over time method used description				Management determined that property and asset management and construction and development management services each represent a series of stand-ready performance obligations satisfied over time with each day of service being a distinct performance obligation.
Number of real estate properties leased | Property		50		50
Number of wholly owned properties acquired | Property		194		194
Number of joint venture properties acquired | JointVenture				27
Number of states in properties located | State		45		45
Right-of-use assets		$ 19,100,000		$ 19,100,000		$ 8,600,000
Lease liabilities		8,600,000		8,600,000		$ 8,600,000
ASU 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Right-of-use assets							$ 8,400,000
Lease liabilities							$ 8,400,000
Capitalized internal leasing and legal leasing costs				1,300,000
Below-market lease right of use asset		11,005		11,005
Class C Common Shares [Member]
Summary Of Significant Accounting Policies [Line Items]
Common shares, outstanding | shares			1,000		1,000				0	372,000	3,151,000
Interest Rate Cap [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest rate caps purchased		5,000,000.0		$ 5,000,000.0
Derivative, term of contract				4 years
Notional amount		1,261,000,000		$ 1,261,000,000
Derivative strike rate				3.50%
Interest rate caps outstanding		0		$ 0				$ 0
Derivative gain (loss)		$ 0	$ (200,000)	$ 0	$ (7,000)
Sears Holdings Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Right to recapture property space		100.00%		100.00%
Number of joint venture properties acquired | JointVenture	3
Management and Other Fee Income [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue earned from unconsolidated joint ventures				100.00%
Real Estate Assets Four Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest sold in number of properties | Property		4
Gain on sale of real estate		$ 4,400,000
Real Estate Assets Eleven Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Interest sold in number of properties | Property				11
Gain on sale of real estate				$ 22,100,000
Real Estate Assets, Land Parcel [Member]
Summary Of Significant Accounting Policies [Line Items]
Gain on sale of real estate				$ 7,200,000
Number of parcels of land, sale in exchange transaction | Parcel				1
Number of parcels of land, purchase in exchange transaction | Parcel				2
Operating Partnership [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of operating partnership interest held by parent		66.00%		66.00%