Real Estate Facilities (Narrative) (Details) $ in Thousands		6 Months Ended	12 Months Ended
	Jan. 07, 2020 USD ($) ft²	Jun. 30, 2020 USD ($) ft² a item property	Dec. 31, 2019 ft² item	Aug. 04, 2020	Jan. 10, 2020 USD ($) ft²	Jun. 30, 2019 USD ($)	Apr. 18, 2019 USD ($) ft²
Real Estate Facilities [Line Items]
Number of units to be developed | property		395
Area of land (in acres) | a		5
Area of real estate property (in square feet) | ft²		628,000
Committed transaction costs for executed leases		$ 12,300
Purchase price		$ 13,513				$ 13,824
Number of buildings | item		674
Proceeds from sale of real estate facility		$ 29,266
Gain on sale of real estate facility		$ 19,621
La Mirada Acquisition [Member]
Real Estate Facilities [Line Items]
Area of real estate property (in square feet) | ft²					73,000
Purchase price					$ 13,500
Signal Hill Acquisition [Member]
Real Estate Facilities [Line Items]
Area of real estate property (in square feet) | ft²							74,000
Purchase price							$ 13,800
Metro Park North [Member]
Real Estate Facilities [Line Items]
Area of real estate property (in square feet) | ft²	113,000
Proceeds from sale of real estate facility	$ 29,300
Gain on sale of real estate facility	$ 19,600
Properties Held for Sale [Member]
Real Estate Facilities [Line Items]
Area of real estate property (in square feet) | ft²		40,000	40,000
Number of buildings | item		2	2
Investment in Joint Venture [Member]
Real Estate Facilities [Line Items]
Economic interest in joint venture, percentage		95.00%
Investment in Joint Venture [Member] | Subsequent Event [Member]
Real Estate Facilities [Line Items]
Economic interest in joint venture, percentage				98.20%
JV Partner [Member]
Real Estate Facilities [Line Items]
Economic interest in joint venture, percentage		5.00%
JV Partner [Member] | Investment in Joint Venture [Member] | Subsequent Event [Member]
Real Estate Facilities [Line Items]
Economic interest in joint venture, percentage				1.80%