Real Estate Facilities (Narrative) (Details) $ in Thousands			3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 16, 2020 USD ($) item	Jan. 07, 2020 USD ($) ft²	Sep. 30, 2020 USD ($) ft² a	Sep. 30, 2020 USD ($) ft² a item property	Dec. 31, 2019 ft² item	Jan. 10, 2020 USD ($) ft²	Sep. 30, 2019 USD ($)	Sep. 05, 2019 USD ($) ft²	Apr. 18, 2019 USD ($) ft²
Real Estate Facilities [Line Items]
Area of land (in acres) | a			44.5	44.5
Rentable area (in square feet) | ft²			27,500,000	27,500,000
Committed transaction costs for executed leases				$ 11,200
Purchase price			$ 13,513	$ 13,513			$ 118,154
Number of buildings | item				672
Proceeds from sale of real estate facilities				$ 40,674
Gain on sale of real estate facilities			$ 7,652	$ 27,273
La Mirada Acquisition [Member]
Real Estate Facilities [Line Items]
Rentable area (in square feet) | ft²						73,000
Purchase price						$ 13,500
Santa Fe Springs Acquisition [Member]
Real Estate Facilities [Line Items]
Rentable area (in square feet) | ft²								543,000
Purchase price								$ 104,300
Signal Hill Acquisition [Member]
Real Estate Facilities [Line Items]
Rentable area (in square feet) | ft²									74,000
Purchase price									$ 13,800
Metro Park North [Member]
Real Estate Facilities [Line Items]
Rentable area (in square feet) | ft²		113,000
Proceeds from sale of real estate facilities		$ 29,300
Gain on sale of real estate facilities		$ 19,600
Industrial Property [Member]
Real Estate Facilities [Line Items]
Area of real estate property (in square feet) | ft²			83,000	83,000
Development costs incurred			$ 6,100	$ 6,100
Estimated development costs			$ 8,100	$ 8,100
Properties Held for Sale [Member]
Real Estate Facilities [Line Items]
Rentable area (in square feet) | ft²					40,000
Number of buildings | item					2
Highgate at the Mile [Member]
Real Estate Facilities [Line Items]
Number of units to be developed | property				395
Area of land (in acres) | a			5	5
Highgate at the Mile [Member] | Investment in Joint Venture [Member]
Real Estate Facilities [Line Items]
Economic interest in joint venture, percentage			95.00%	95.00%
Highgate at the Mile [Member] | JV Partner [Member]
Real Estate Facilities [Line Items]
Economic interest in joint venture, percentage			5.00%	5.00%
Redmond, WA [Member] | Industrial Property [Member]
Real Estate Facilities [Line Items]
Rentable area (in square feet) | ft²			40,000	40,000
Number of buildings | item	2
Proceeds from sale of real estate facilities	$ 11,400
Gain on sale of real estate facilities	$ 7,700