Investments in Real Estate - Summary of Acquired Wholly Owned Industrial Properties (Detail) $ in Thousands		9 Months Ended
	Apr. 28, 2017 USD ($)	Sep. 30, 2017 USD ($) ft² building	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Rentable Square Feet | ft²		3,582,375
Number of Buildings | building		39
Purchase Price		$ 534,472
Capitalized acquisition costs		1,400
Payments to acquire real estate		532,108	$ 308,277
Principal amount		666,979		$ 502,476
$125M senior notes
Business Acquisition [Line Items]
Principal amount		$ 125,000		$ 0
28903 Avenue Paine
Business Acquisition [Line Items]
Date of Acquisition		Feb. 17, 2017
Rentable Square Feet | ft²		111,346
Number of Buildings | building		1
Purchase Price		$ 17,060
2390 Ward Avenue
Business Acquisition [Line Items]
Date of Acquisition		Apr. 28, 2017
Rentable Square Feet | ft²		138,700
Number of Buildings | building		1
Purchase Price		$ 16,499
Safari Business Center
Business Acquisition [Line Items]
Date of Acquisition		May 24, 2017
Rentable Square Feet | ft²		1,138,090
Number of Buildings | building		16
Purchase Price		$ 141,200
4175 Conant Street
Business Acquisition [Line Items]
Date of Acquisition		Jun. 14, 2017
Rentable Square Feet | ft²		142,593
Number of Buildings | building		1
Purchase Price		$ 30,600
5421 Argosy Avenue
Business Acquisition [Line Items]
Date of Acquisition		Jun. 15, 2017
Rentable Square Feet | ft²		35,321
Number of Buildings | building		1
Purchase Price		$ 5,300
14820-14830 Carmenita Road
Business Acquisition [Line Items]
Date of Acquisition		Jun. 30, 2017
Rentable Square Feet | ft²		198,062
Number of Buildings | building		3
Purchase Price		$ 30,650
3002-3072 Inland Empire Blvd
Business Acquisition [Line Items]
Date of Acquisition		Jul. 03, 2017
Rentable Square Feet | ft²		218,407
Number of Buildings | building		4
Purchase Price		$ 26,900
17000 Kingsview Avenue
Business Acquisition [Line Items]
Date of Acquisition		Jul. 11, 2017
Rentable Square Feet | ft²		100,121
Number of Buildings | building		1
Purchase Price		$ 13,986
Rancho Pacifica Park
Business Acquisition [Line Items]
Date of Acquisition		Jul. 18, 2017
Rentable Square Feet | ft²		1,170,806
Number of Buildings | building		6
Purchase Price		$ 210,500
11190 White Birch Drive
Business Acquisition [Line Items]
Date of Acquisition		Jul. 20, 2017
Rentable Square Feet | ft²		201,035
Number of Buildings | building		1
Purchase Price		$ 19,810
4832-4850 Azusa Canyon Road
Business Acquisition [Line Items]
Date of Acquisition		Jul. 28, 2017
Rentable Square Feet | ft²		87,421
Number of Buildings | building		1
Purchase Price		$ 14,550
1825 Soto Street
Business Acquisition [Line Items]
Date of Acquisition		Sep. 08, 2017
Rentable Square Feet | ft²		25,040
Number of Buildings | building		2
Purchase Price		$ 3,475
19402 Susana Street
Business Acquisition [Line Items]
Date of Acquisition		Sep. 13, 2017
Rentable Square Feet | ft²		15,433
Number of Buildings | building		1
Purchase Price		$ 3,942
9375 Archibald Avenue
Business Acquisition [Line Items]
Payments to acquire real estate	$ 6,500
2535 Midway Drive
Business Acquisition [Line Items]
Payments to acquire real estate		$ 39,700