Investments in Real Estate - Acquisitions - Additional Information (Detail) $ in Thousands						3 Months Ended	12 Months Ended
	Jul. 06, 2016 USD ($)	May 03, 2016 USD ($)	Apr. 15, 2016 USD ($) shares	Feb. 03, 2015 shares	Aug. 19, 2014 shares	Dec. 31, 2016 USD ($) ft² property shares	Dec. 31, 2016 USD ($) ft² property building shares	Dec. 31, 2015 USD ($) a property building shares	Dec. 31, 2014 USD ($)	Apr. 11, 2016 ft² property	Feb. 25, 2014 USD ($)
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Shares outstanding | shares						3,600,000	3,600,000	0
Preferred stock, interest							5.875%	5.875%
Rentable Square Feet						3,372,794	3,372,794	2,129,753
Number of Buildings | building							30	39
Contractual Purchase Price (in thousands)							$ 371,682	$ 247,579
Issuance of common stock, shares | shares				11,500,000	17,250,000
Payments to Acquire Real Estate							367,621	230,599	$ 383,662
Proceeds from sale of real estate							$ 38,505	0	$ 15,410
Number of real estate properties | property						136	136
Deposits paid											$ 1,400
Debt assumed						$ 0	$ 0	17,097
Deferred rent liability						$ 0	$ 0	$ 977
8525 Camino Santa Fe [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							San Diego - Central
Date of Acquisition							Mar. 15, 2016
Rentable Square Feet | ft²						59,399	59,399
Number of Buildings | building							1
Contractual Purchase Price (in thousands)							$ 8,450
28454 Livingston Avenue [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Los Angeles - San Fernando Valley
Date of Acquisition							Mar. 29, 2016
Rentable Square Feet | ft²						134,287	134,287
Number of Buildings | building							1
Contractual Purchase Price (in thousands)							$ 16,000
REIT Portfolio Acquisition [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Various(2)
Date of Acquisition							Apr. 15, 2016
Rentable Square Feet | ft²						1,530,814	1,530,814			1,530,814
Number of Buildings | building							9
Contractual Purchase Price (in thousands)							$ 191,000
Number of real estate properties | property										9
Number of properties acquired | property								9
10750-10826 Lower Azusa Road
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Los Angeles - San Gabriel Valley
Date of Acquisition							May 03, 2016
Rentable Square Feet | ft²						79,050	79,050
Number of Buildings | building							4
Contractual Purchase Price (in thousands)							$ 7,660
Payments to Acquire Real Estate		$ 2,500
525 Park Avenue [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Los Angeles - San Fernando Valley
Date of Acquisition							Jun. 30, 2016
Rentable Square Feet | ft²						63,403	63,403
Number of Buildings | building							1
Contractual Purchase Price (in thousands)							$ 7,550
3255 Mission Oaks Blvd
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Ventura
Date of Acquisition							Jul. 06, 2016
Rentable Square Feet | ft²						457,693	457,693
Number of Buildings | building							1
Contractual Purchase Price (in thousands)							$ 25,700
Payments to Acquire Real Estate	$ 25,700
Percentage of voting interests acquired	85.00%					100.00%	100.00%
1600 E. Orangethorpe Avenue [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Orange County - North
Date of Acquisition							Aug. 24, 2016
Rentable Square Feet | ft²						345,756	345,756
Number of Buildings | building							6
Contractual Purchase Price (in thousands)							$ 40,137
14742-14750 Nelson Avenue [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Los Angeles - San Gabriel Valley
Date of Acquisition							Sep. 08, 2016
Rentable Square Feet | ft²						145,531	145,531
Number of Buildings | building							2
Contractual Purchase Price (in thousands)							$ 15,000
3927 Oceanic Drive [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							San Diego - North County
Date of Acquisition							Oct. 21, 2016
Rentable Square Feet | ft²						54,740	54,740
Number of Buildings | building							1
Contractual Purchase Price (in thousands)							$ 7,200
301-445 North Figueroa in Wilmington, California [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Los Angeles - South Bay
Date of Acquisition							Nov. 04, 2016
Rentable Square Feet | ft²						133,925	133,925
Number of Buildings | building							1
Contractual Purchase Price (in thousands)							$ 13,000
12320 4th Street [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							Inland Empire - West
Date of Acquisition							Dec. 07, 2016
Rentable Square Feet | ft²						284,676	284,676
Number of Buildings | building							2
Contractual Purchase Price (in thousands)							$ 24,435
9190 Activity Road [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket							San Diego - Central
Date of Acquisition							Dec. 16, 2016
Rentable Square Feet | ft²						83,520	83,520
Number of Buildings | building							1
Contractual Purchase Price (in thousands)							$ 15,550
8902-8940 Activity Road
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								San Diego - Central
Date of Acquisition								Jan. 21, 2015
Rentable Square Feet | a								112,501
Number of Buildings | building								5
Contractual Purchase Price (in thousands)								$ 18,450
12907 Imperial Highway
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Mid-counties
Date of Acquisition								Jan. 21, 2015
Rentable Square Feet | a								101,080
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 12,180
Deposits paid								2,100
Debt assumed								5,400
Fair value premium of assumed debt								$ 500
1210 North Red Gum Street
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Orange County - North
Date of Acquisition								Mar. 09, 2015
Rentable Square Feet | a								64,570
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 7,650
9401 De Soto Avenue
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - San Fernando Valley
Date of Acquisition								Mar. 18, 2015
Rentable Square Feet | a								150,263
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 14,075
9615 Norwalk Boulevard
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Mid-counties
Date of Acquisition								Apr. 30, 2015
Rentable Square Feet | a								38,362
Number of Buildings | building								2
Contractual Purchase Price (in thousands)								$ 9,642
16221 Arthur Street
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Mid-counties
Date of Acquisition								May 01, 2015
Rentable Square Feet | a								61,372
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 5,774
2588 And 2605 Industry Way
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - South Bay
Date of Acquisition								May 12, 2015
Rentable Square Feet | a								164,662
Number of Buildings | building								2
Contractual Purchase Price (in thousands)								$ 22,000
425 South Hacienda Boulevard
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - San Gabriel Valley
Date of Acquisition								May 15, 2015
Rentable Square Feet | a								51,823
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 7,000
6700 Alameda Street
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Central LA
Date of Acquisition								Jun. 29, 2015
Rentable Square Feet | a								78,280
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 14,500
12720-12860 Danielson Court
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								San Diego - Central
Date of Acquisition								Jul. 10, 2015
Rentable Square Feet | a								112,062
Number of Buildings | building								6
Contractual Purchase Price (in thousands)								$ 16,900
10950 Norwalk Boulevard
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Mid-counties
Date of Acquisition								Jul. 29, 2015
Rentable Square Feet | a								18,995
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 4,973
610-760 Hueneme Road
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Ventura
Date of Acquisition								Aug. 11, 2015
Rentable Square Feet | a								86,904
Number of Buildings | building								2
Contractual Purchase Price (in thousands)								$ 9,607
10709-10719 Norwalk Boulevard
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Mid-counties
Date of Acquisition								Sep. 01, 2015
Rentable Square Feet | a								58,056
Number of Buildings | building								2
Contractual Purchase Price (in thousands)								$ 7,242
6020 Sheila Street
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Central LA
Date of Acquisition								Sep. 18, 2015
Rentable Square Feet | a								70,877
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 12,220
9805 6th Street
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Inland Empire West
Date of Acquisition								Sep. 30, 2015
Rentable Square Feet | a								81,377
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 6,894
16321-16327 Arrow Hwy
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - San Gabriel Valley
Date of Acquisition								Oct. 14, 2015
Rentable Square Feet | a								64,296
Number of Buildings | building								3
Contractual Purchase Price (in thousands)								$ 8,120
2535 Midway Drive
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								San Diego - Central
Date of Acquisition								Oct. 22, 2015
Rentable Square Feet | a								373,744
Number of Buildings | building								2
Contractual Purchase Price (in thousands)								$ 19,295
601-605 Milliken Avenue
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Inland Empire West
Date of Acquisition								Dec. 08, 2015
Rentable Square Feet | a								128,322
Number of Buildings | building								3
Contractual Purchase Price (in thousands)								$ 13,000
1065 E. Walnut Street
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - South Bay
Date of Acquisition								Dec. 11, 2015
Rentable Square Feet | a								172,420
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 16,700
Debt assumed								10,900
Fair value premium of assumed debt								$ 300
12247 Lakeland Road
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Los Angeles - Mid-counties
Date of Acquisition								Dec. 16, 2015
Rentable Square Feet | a								24,875
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 4,257
17311 Nichols Lane
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Submarket								Orange County - West
Date of Acquisition								Dec. 30, 2015
Rentable Square Feet | a								114,912
Number of Buildings | building								1
Contractual Purchase Price (in thousands)								$ 17,100
Common Stock | REIT Portfolio Acquisition [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Percentage of voting interests acquired			100.00%
12.5% Preferred Stock | REIT Portfolio Acquisition [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Shares outstanding | shares			575
Preferred Stock, Shares Issued | shares			700
Preferred stock, interest			12.50%
Preferred Stock, Redemption Amount			$ 125
Unaffiliated Third Parties | 12.5% Preferred Stock | REIT Portfolio Acquisition [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Shares outstanding | shares			125
22343-22349 La Palma Avenue And 157th Street
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Proceeds from sale of real estate	$ 18,000					$ 18,100
Follow On Public Offer (Equity Offering)
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Issuance of common stock, shares | shares			10,350,000
Follow On Public Offer (Equity Offering) | REIT Portfolio Acquisition [Member]
Disclosure Investment In Real Estate Acquisitions Additional Information Detail [Line Items]
Issuance of common stock, shares | shares			10,350,000