Investments in Real Estate - Schedule of Details of Properties Acquired (Detail) (Parenthetical)	1 Months Ended
	Jan. 31, 2018 Property	Nov. 30, 2017 Property	Dec. 31, 2018 Property Bed	Dec. 31, 2017 ft² Property
Real Estate Properties [Line Items]
Number of Properties			359	115
Multifamily [Member]
Real Estate Properties [Line Items]
Number of Properties			73	48
Multifamily [Member] | Emory Point [Member]
Real Estate Properties [Line Items]
Area of retail space | ft²				124,000
Industrial [Member]
Real Estate Properties [Line Items]
Number of Properties			270	55
Hotel [Member]
Real Estate Properties [Line Items]
Number of Properties			15	10
Penn State University [Member] | Multifamily [Member] | EdR Student Housing Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			15.00%
University of Arizona [Member] | Multifamily [Member] | EdR Student Housing Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			10.00%
University of Virginia [Member] | Multifamily [Member] | EdR Student Housing Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			8.00%
Arizona State University [Member] | Multifamily [Member] | EdR Student Housing Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			8.00%
Virginia Tech [Member] | Multifamily [Member] | EdR Student Housing Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			8.00%
Various [Member] | Multifamily [Member] | Aston Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Number of properties closed	8	12
Number of Properties			8	12
Various [Member] | Multifamily [Member] | Wave Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties			6
Various [Member] | Multifamily [Member] | Southwest MH [Member]
Real Estate Properties [Line Items]
Number of Properties			14
Various [Member] | Multifamily [Member] | EdR Student Housing Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties			20
Number of beds | Bed			10,610
Various [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties				6
Number of floor property				32
Number of garden style properties				5
Various [Member] | Multifamily [Member] | ACG II Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties				4
Number of garden style properties				4
Various [Member] | Industrial [Member] | Canyon Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties			146
Various [Member] | Industrial [Member] | HP Cold Storage Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties			6
Various [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties			106
Various [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties				38
Various [Member] | Industrial [Member] | Southeast Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties				5
Various [Member] | Hotel [Member] | Corporex Select Service Portfolio [Member]
Real Estate Properties [Line Items]
Number of Properties			5
Austin/San Antonio, TX [Member] | Multifamily [Member] | Aston Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			47.00%	49.00%
Dallas/Fort Worth, TX [Member] | Multifamily [Member] | Aston Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			21.00%	25.00%
Nashville, TN [Member] | Multifamily [Member] | Aston Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			18.00%	22.00%
Nashville, TN [Member] | Industrial [Member] | Southeast Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				21.00%
Louisville, KY [Member] | Multifamily [Member] | Aston Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			14.00%	4.00%
Chicago, IL [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				19.00%
Chicago, IL [Member] | Industrial [Member] | Canyon Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			19.00%
Chicago, IL [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				23.00%
Dallas, TX [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				14.00%
Dallas, TX [Member] | Industrial [Member] | Canyon Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			15.00%
Dallas, TX [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				10.00%
Indianapolis, IN [Member] | Industrial [Member] | Canyon Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			11.00%
Baltimore/Washington, D.C. [Member] | Industrial [Member] | Canyon Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			9.00%
Columbus, OH [Member] | Industrial [Member] | Canyon Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			7.00%
Greater Seattle, WA [Member] | Multifamily [Member] | Wave Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			29.00%
Sacramento, CA [Member] | Multifamily [Member] | Wave Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			28.00%
Las Vegas, NV [Member] | Multifamily [Member] | Wave Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			22.00%
Spokane, WA [Member] | Multifamily [Member] | Wave Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			14.00%
Portland, OR [Member] | Multifamily [Member] | Wave Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			7.00%
Stockton, CA [Member] | Industrial [Member] | HP Cold Storage Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			52.00%
Atlanta, GA [Member] | Industrial [Member] | HP Cold Storage Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			24.00%
Atlanta, GA [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			9.00%
Atlanta, GA [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				38.00%
Atlanta, GA [Member] | Industrial [Member] | Southeast Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				26.00%
Baltimore, MD [Member] | Industrial [Member] | HP Cold Storage Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			18.00%
Austin, TX [Member] | Industrial [Member] | HP Cold Storage Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			6.00%
Phoenix, AZ [Member] | Multifamily [Member] | Southwest MH [Member]
Real Estate Properties [Line Items]
Percentage of leased property			86.00%
Phoenix, AZ [Member] | Hotel [Member] | Corporex Select Service Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			24.00%
San Diego, CA [member] | Multifamily [Member] | Southwest MH [Member]
Real Estate Properties [Line Items]
Percentage of leased property			11.00%
Palm Desert, CA [Member] | Multifamily [Member] | Southwest MH [Member]
Real Estate Properties [Line Items]
Percentage of leased property			3.00%
Reno, NV [Member] | Hotel [Member] | Corporex Select Service Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			23.00%
Salt Lake City, UT [Member] | Hotel [Member] | Corporex Select Service Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			20.00%
Sonoma, CA [Member] | Hotel [Member] | Corporex Select Service Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			17.00%
Tampa, FL [Member] | Hotel [Member] | Corporex Select Service Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			16.00%
Memphis, TN [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			23.00%
Orlando FL [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			19.00%
Jacksonville, FL [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			10.00%
Jacksonville, FL [Member] | Industrial [Member] | Southeast Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				53.00%
Richmond, VA [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			7.00%
Winston-Salem, NC [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property			7.00%
Downtown Orlando, FL [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				19.00%
Palm Beach Gardens, FL [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				19.00%
Houston, TX [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				17.00%
Orlando, FL [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				17.00%
Orlando, FL [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				2.00%
Harrisburg, PA [Member] | Industrial [Member] | HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				10.00%
Kansas City, KS [Member] | Multifamily [Member] | TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				12.00%
Gilbert, AZ [Member] | Multifamily [Member] | ACG II Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				30.00%
Modesto, CA [Member] | Multifamily [Member] | ACG II Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				25.00%
Olympia, WA [Member] | Multifamily [Member] | ACG II Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				24.00%
Flagstaff, AZ [Member] | Multifamily [Member] | ACG II Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Percentage of leased property				21.00%