Investments in Real Estate - Schedule of Details of Properties Acquired (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2017 USD ($) Property
Real Estate Properties [Line Items]
Number of Properties	85
Purchase Price | $	$ 2,371,908
Hotel [Member]
Real Estate Properties [Line Items]
Number of Properties	7
Multifamily [Member]
Real Estate Properties [Line Items]
Number of Properties	27
Industrial [Member]
Real Estate Properties [Line Items]
Number of Properties	50
Retail [Member]
Real Estate Properties [Line Items]
Number of Properties	1
CA [Member] | Hotel [Member] | Hyatt Place UC Davis [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Jan. 31, 2017
Purchase Price | $	$ 32,687
CA [Member] | Hotel [Member] | Hyatt Place San Jose Downtown [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Jun. 30, 2017
Purchase Price | $	$ 65,321
CA [Member] | Industrial [Member] | Stockton [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Feb. 28, 2017
Purchase Price | $	$ 32,751
AZ [Member] | Multifamily [Member] | Sonora Canyon [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Feb. 28, 2017
Purchase Price | $	$ 40,983
AZ [Member] | Multifamily [Member] | Gilbert Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest	90.00%
Number of Properties	2
Acquisition Date	Sep. 30, 2017
Purchase Price | $	$ 147,039
Philadelphia, PA [Member] | Retail [Member] | Bakers Centre [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Mar. 31, 2017
Purchase Price | $	$ 54,223
Various [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	6
Acquisition Date	Apr. 30, 2017
Purchase Price | $	$ 432,593
Various [Member] | Multifamily [Member] | ACG II Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	94.00%
Number of Properties	4
Acquisition Date	Sep. 30, 2017
Purchase Price | $	$ 148,038
Various [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	38
Acquisition Date	Apr. 30, 2017
Purchase Price | $	$ 405,930
Atlanta, GA [Member] | Hotel [Member] | Hyatt House Downtown Atlanta [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Aug. 31, 2017
Purchase Price | $	$ 35,332
Atlanta, GA [Member] | Multifamily [Member] | Emory Point [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	May 31, 2017
Purchase Price | $	$ 201,578
NV [Member] | Multifamily [Member] | Nevada West [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	3
Acquisition Date	May 31, 2017
Purchase Price | $	$ 170,965
NV [Member] | Multifamily [Member] | Mountain Gate & Trails [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	2
Acquisition Date	Jun. 30, 2017
Purchase Price | $	$ 83,572
NV [Member] | Multifamily [Member] | Elysian West [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Jul. 31, 2017
Purchase Price | $	$ 107,027
Tampa & Orlando, FL [Member] | Hotel [Member] | Florida Select-Service 4-Pack [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	4
Acquisition Date	Jul. 31, 2017
Purchase Price | $	$ 58,973
Dallas, TX [Member] | Multifamily [Member] | Harbor 5 [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	5
Acquisition Date	Aug. 31, 2017
Purchase Price | $	$ 146,161
Dallas, TX [Member] | Multifamily [Member] | Domain & GreenVue Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	2
Acquisition Date	Sep. 30, 2017
Purchase Price | $	$ 134,452
Fairfield, NJ [Member] | Industrial [Member] | Fairfield Industrial [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	11
Acquisition Date	Sep. 30, 2017
Purchase Price | $	$ 74,283