Summary of Significant Accounting Policies - Additional Information (Detail)		3 Months Ended
	Jun. 11, 2015 JointVenture	Mar. 31, 2019 USD ($) Property JointVenture State Segment	Mar. 31, 2018 USD ($) shares	Jan. 01, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 29, 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
Interest sold in number of properties | Property		8
Net proceeds from sale of real estate		$ 37,569,000	60,435,000
Gain on sale of real estate		21,261,000	41,831,000
Real estate held for sale, assets		7,510,000			$ 3,094,000
Real estate held for sale, liabilities		0			0
Impairment loss		0	0
Restricted cash		$ 0	$ 177,419,000
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 wholly owned properties acquired | Property		198
Number of joint venture properties acquired | JointVenture		27
Number of states in properties located | State		46
Right-of-use assets		$ 8,600,000
Lease liabilies		8,600,000
ASU 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Right-of-use assets				$ 8,400,000
Lease liabilies				$ 8,400,000
Capitalized internal leasing and legal leasing costs		1,300,000
Below-market lease right of use asset		11,005
Class C Common Shares [Member]
Summary Of Significant Accounting Policies [Line Items]
Common shares, outstanding | shares			372,000			0	3,151,000
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%
Interest rate caps outstanding		$ 0			$ 0
Derivative gain		$ 0	$ 200,000
Sears Holdings Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Right to recapture property space		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%
Sale of Seven Properties [Member]
Summary Of Significant Accounting Policies [Line Items]
Net proceeds from sale of real estate		$ 38,800,000
Gain on sale of real estate		$ 21,500,000
Operating Partnership [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of operating partnership interest held by parent		63.90%