Investments in Real Estate - Schedule of Details of Properties Acquired (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Property	Dec. 31, 2017 USD ($) Property
Real Estate Properties [Line Items]
Number of Properties	359	115
Purchase Price | $	$ 7,293,807	$ 3,617,378
Multifamily [Member]
Real Estate Properties [Line Items]
Number of Properties	73	48
Industrial [Member]
Real Estate Properties [Line Items]
Number of Properties	270	55
Hotel [Member]
Real Estate Properties [Line Items]
Number of Properties	15	10
Retail [Member]
Real Estate Properties [Line Items]
Number of Properties	1	2
Various [Member] | Multifamily [Member] | Aston Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	90.00%	90.00%
Number of Properties	8	12
Acquisition Date	Jan. 31, 2018	Nov. 30, 2017
Purchase Price | $	$ 141,743	$ 381,445
Various [Member] | Multifamily [Member] | Wave Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	6
Acquisition Date	May 31, 2018
Purchase Price | $	$ 423,135
Various [Member] | Multifamily [Member] | Southwest MH [Member]
Real Estate Properties [Line Items]
Ownership Interest	99.00%
Number of Properties	14
Acquisition Date	Jun. 30, 2018
Purchase Price | $	$ 176,194
Various [Member] | Multifamily [Member] | EdR Student Housing Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	95.00%
Number of Properties	20
Acquisition Date	Sep. 30, 2018
Purchase Price | $	$ 1,230,857
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] | Canyon Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	146
Acquisition Date	Mar. 31, 2018
Purchase Price | $	$ 1,837,213
Various [Member] | Industrial [Member] | HP Cold Storage Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	6
Acquisition Date	May 31, 2018
Purchase Price | $	$ 253,082
Various [Member] | Industrial [Member] | Meridian Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	106
Acquisition Date	Nov. 30, 2018
Purchase Price | $	$ 962,979
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
Various [Member] | Industrial [Member] | Southeast Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		5
Acquisition Date		Nov. 30, 2017
Purchase Price | $		$ 116,487
Various [Member] | Hotel [Member] | Corporex Select Service Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	5
Acquisition Date	Aug. 31, 2018
Purchase Price | $	$ 117,869
Aurora, IL [Member] | Industrial [Member] | Kraft Chicago Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	3
Acquisition Date	Jan. 31, 2018
Purchase Price | $	$ 151,365
Phoenix, AZ [Member] | Multifamily [Member] | The Boulevard [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Apr. 30, 2018
Purchase Price | $	$ 48,392
Phoenix, AZ [Member] | Multifamily [Member] | Highroads MH [Member]
Real Estate Properties [Line Items]
Ownership Interest	99.00%
Number of Properties	3
Acquisition Date	Apr. 30, 2018
Purchase Price | $	$ 18,637
Phoenix, AZ [Member] | Multifamily [Member] | Evergreen Minari MH [Member]
Real Estate Properties [Line Items]
Ownership Interest	99.00%
Number of Properties	2
Acquisition Date	Jun. 30, 2018
Purchase Price | $	$ 8,614
Phoenix, AZ [Member] | Multifamily [Member] | Velaire At Aspera [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Jul. 31, 2018
Purchase Price | $	$ 64,573
Phoenix, AZ [Member] | Multifamily [Member] | SVPAC MH [Member]
Real Estate Properties [Line Items]
Ownership Interest	99.00%
Number of Properties	2
Acquisition Date	Jul. 31, 2018
Purchase Price | $	$ 14,278
Phoenix, AZ [Member] | Multifamily [Member] | Coyote Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	6
Acquisition Date	Aug. 31, 2018
Purchase Price | $	$ 311,813
Boston, MA [Member] | Multifamily [Member] | Blue Hills Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	May 31, 2018
Purchase Price | $	$ 131,747
Gresham, OR & Turlock, CA [Member] | Multifamily [Member] | ACG III Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest	95.00%
Number of Properties	2
Acquisition Date	May 31, 2018
Purchase Price | $	$ 96,182
Jacksonville & Orlando, FL [Member] | Multifamily [Member] | Carroll Florida Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	2
Acquisition Date	May 31, 2018
Purchase Price | $	$ 116,832
Henderson, NV [Member] | Hotel [Member] | Henderson Select-Service 2-Pack [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	2
Acquisition Date	May 31, 2018
Purchase Price | $	$ 36,260
Orlando, FL [Member] | Hotel [Member] | Orlando Select-Service 2-Pack [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	2
Acquisition Date	May 31, 2018
Purchase Price | $	$ 48,862
Las Vegas, NV [Member] | Multifamily [Member] | Solis at Flamingo [Member]
Real Estate Properties [Line Items]
Ownership Interest	95.00%
Number of Properties	1
Acquisition Date	Jun. 30, 2018
Purchase Price | $	$ 72,560
Las Vegas, NV [Member] | Multifamily [Member] | Royal Vegas, MH [Member]
Real Estate Properties [Line Items]
Ownership Interest	99.00%
Number of Properties	1
Acquisition Date	Oct. 31, 2018
Purchase Price | $	$ 8,372
Las Vegas, NV [Member] | Multifamily [Member] | Avanti Apartments [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Dec. 31, 2018
Purchase Price | $	$ 69,008
Las Vegas, NV [Member] | Multifamily [Member] | Nevada West Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		3
Acquisition Date		May 31, 2017
Purchase Price | $		$ 170,965
Las Vegas, NV [Member] | Multifamily [Member] | Mountain Gate & Trails Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		2
Acquisition Date		Jun. 30, 2017
Purchase Price | $		$ 83,572
Las Vegas, NV [Member] | Multifamily [Member] | Elysian West Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Jul. 31, 2017
Purchase Price | $		$ 107,027
Las Vegas, NV [Member] | Multifamily [Member] | Talavera and Flamingo Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		2
Acquisition Date		Dec. 31, 2017
Purchase Price | $		$ 115,427
Desert Hot Springs, CA [Member] | Multifamily [Member] | Hidden Springs MH [Member]
Real Estate Properties [Line Items]
Ownership Interest	99.00%
Number of Properties	1
Acquisition Date	Jul. 31, 2018
Purchase Price | $	$ 17,122
San Antonio, TX [Member] | Hotel [Member] | JW Marriott San Antonio Hill Country Resort [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Aug. 31, 2018
Purchase Price | $	$ 604,323
Miami FL [Member] | Multifamily [Member] | Signature at Kendall Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Dec. 31, 2017
Purchase Price | $		$ 139,468
Miami FL [Member] | Retail [Member] | Vista Center [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Aug. 31, 2018
Purchase Price | $	$ 34,738
Seattle, WA [Member] | Hotel [Member] | Hampton Inn & Suites Federal Way [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Oct. 31, 2018
Purchase Price | $	$ 33,672
Reno, NV [Member] | Hotel [Member] | Staybridge Suites Reno [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Nov. 30, 2018
Purchase Price | $	$ 17,964
Salt Lake City, UT [Member] | Hotel [Member] | Salt Lake City Select Service 3 Pack [Member]
Real Estate Properties [Line Items]
Ownership Interest	60.00%
Number of Properties	3
Acquisition Date	Nov. 30, 2018
Purchase Price | $	$ 104,508
Stockton, CA [Member] | Industrial [Member] | Stockton Distribution Center [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	1
Acquisition Date	Dec. 31, 2018
Purchase Price | $	$ 94,285
Atlanta, GA [Member] | Industrial [Member] | Summit Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest	100.00%
Number of Properties	8
Acquisition Date	Dec. 31, 2018
Purchase Price | $	$ 40,463
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
Tavares, FL [Member] | Multifamily [Member] | Riverest MH [Member]
Real Estate Properties [Line Items]
Ownership Interest	99.00%
Number of Properties	1
Acquisition Date	Dec. 31, 2018
Purchase Price | $	$ 6,165
Davis, 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
Mesa, AZ [Member] | Multifamily [Member] | Sonora Canyon Apartments [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Feb. 28, 2017
Purchase Price | $		$ 40,983
Stockton, CA [Member] | Industrial [Member] | Stockton Industrial Park [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Feb. 28, 2017
Purchase Price | $		$ 32,751
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
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
San Jose, 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
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 Multifamily [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
Gilbert, 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
Fairfield, NJ [Member] | Industrial [Member] | Fairfield Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		11
Acquisition Date		Sep. 30, 2017
Purchase Price | $		$ 74,283
Burbank, CA [Member] | Retail [Member] | Plaza Del Sol Retail [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Oct. 31, 2017
Purchase Price | $		$ 45,898
Boston & Worcester, MA [Member] | Hotel [Member] | Boston/Worcester Select-Service 3-Pack [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		3
Acquisition Date		Oct. 31, 2017
Purchase Price | $		$ 81,762
Jacksonville, FL [Member] | Multifamily [Member] | Olympus Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest		95.00%
Number of Properties		3
Acquisition Date		Nov. 30, 2017
Purchase Price | $		$ 142,129
Hillsboro, OR [Member] | Multifamily [Member] | Amberglen West Multifamily [Member]
Real Estate Properties [Line Items]
Ownership Interest		100.00%
Number of Properties		1
Acquisition Date		Nov. 30, 2017
Purchase Price | $		$ 95,035
Everet, WA and Thornton, CO [Member] | Multifamily [Member] | Walden Pond & Montair Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Ownership Interest		95.00%
Number of Properties		2
Acquisition Date		Dec. 31, 2017
Purchase Price | $		$ 127,819