Investments in Real Estate - Schedule of Purchase Price Allocation of Properties (Detail) $ in Thousands	Jun. 30, 2017 USD ($)
Real Estate Properties [Line Items]
Building and building improvements	$ 1,224,870
Land and land improvements	194,692
Furniture, fixtures and equipment	19,347
Intangible assets	93,242
Below-market lease intangibles	(11,548)
Total purchase price	1,520,603
In-place Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	69,461
Below-market Ground Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	4,683
Above-market Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	2,984
Prepaid Ground Lease Rent [Member]
Real Estate Properties [Line Items]
Intangible assets	16,114
TA Multifamily Portfolio [Member]
Real Estate Properties [Line Items]
Building and building improvements	337,889
Land and land improvements	68,456
Furniture, fixtures and equipment	4,651
Below-market lease intangibles	(307)
Total purchase price	432,593
TA Multifamily Portfolio [Member] | In-place Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	21,880
TA Multifamily Portfolio [Member] | Above-market Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	24
HS Industrial Portfolio [Member]
Real Estate Properties [Line Items]
Building and building improvements	345,391
Land and land improvements	45,081
Below-market lease intangibles	(8,061)
Total purchase price	405,930
HS Industrial Portfolio [Member] | In-place Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	20,793
HS Industrial Portfolio [Member] | Above-market Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	2,726
Emory Point [Member]
Real Estate Properties [Line Items]
Building and building improvements	171,709
Furniture, fixtures and equipment	3,040
Below-market lease intangibles	(576)
Total purchase price	201,578
Emory Point [Member] | In-place Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	11,207
Emory Point [Member] | Above-market Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	84
Emory Point [Member] | Prepaid Ground Lease Rent [Member]
Real Estate Properties [Line Items]
Intangible assets	16,114
Nevada West [Member]
Real Estate Properties [Line Items]
Building and building improvements	145,305
Land and land improvements	17,409
Furniture, fixtures and equipment	2,833
Total purchase price	170,965
Nevada West [Member] | In-place Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	5,418
All Other [Member]
Real Estate Properties [Line Items]
Building and building improvements	224,576
Land and land improvements	63,746
Furniture, fixtures and equipment	8,823
Below-market lease intangibles	(2,604)
Total purchase price	309,537
All Other [Member] | In-place Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	10,163
All Other [Member] | Below-market Ground Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	4,683
All Other [Member] | Above-market Lease Intangibles [Member]
Real Estate Properties [Line Items]
Intangible assets	$ 150