Investments in Real Estate - Narrative (Details) $ in Thousands		12 Months Ended
	Dec. 19, 2019 USD ($) ft² building	Dec. 31, 2020 USD ($) property	Dec. 31, 2020 property	Dec. 31, 2020 ft² property	Dec. 31, 2020 a property	Dec. 31, 2019 USD ($) ft² a property	Dec. 31, 2018 USD ($)	Dec. 31, 2020 ft²	Dec. 31, 2020 a	Dec. 31, 2020 building
Finite-Lived Intangible Assets [Line Items]
Revenues		$ 186,884				$ 171,022	$ 151,657
Net income		$ 79,795				55,516	63,289
Number of properties	17	222	222	222	222
Area of real estate property | ft²	699,104
Asset acquisition, consideration transferred	$ 273,610
Capitalized interest associated with redevelopment activities		$ 1,600				3,200	$ 2,500
Seattle
Finite-Lived Intangible Assets [Line Items]
Number of properties | property		1	1	1	1
Improved land parcels
Finite-Lived Intangible Assets [Line Items]
Number of properties | property		25	25	25	25
Area of real estate property | ft²								13,200,000
Redevelopment property
Finite-Lived Intangible Assets [Line Items]
Number of properties | property		1	1	1	1
Area of real estate property								200,000	91.5
Asset acquisition, consideration transferred		$ 64,100
Asset acquisitions, real estate redevelopment costs		61,400
Redevelopment property | Kent 192 And 6th Avenue South | Seattle
Finite-Lived Intangible Assets [Line Items]
Area of real estate property | ft²								300,000
Asset acquisitions, real estate redevelopment costs		49,800
Asset Acquisitions 2020
Finite-Lived Intangible Assets [Line Items]
Revenues		2,400
Net income		1,100
Asset acquisitions, assets acquired and liabilities assumed, net		100,400
Asset acquisition, intangible assets acquired		4,600
Asset acquisition, intangible liabilities		(2,100)
Asset Acquisitions 2020 | Wholly Owned Properties
Finite-Lived Intangible Assets [Line Items]
Number of properties | building										6
Area of real estate property | ft²								163,794
Asset acquisition, consideration transferred		96,657
Asset Acquisitions 2020 | Industrial property
Finite-Lived Intangible Assets [Line Items]
Area of real estate property acquired				200,000	12.0
Asset Acquisitions 2020 | Improved land parcels
Finite-Lived Intangible Assets [Line Items]
Number of properties acquired | property			5
Asset Acquisitions 2020 | Land
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions		78,800
Asset Acquisitions 2020 | Building
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions		17,000
Asset acquisitions 2019
Finite-Lived Intangible Assets [Line Items]
Revenues		7,600
Net income		$ 3,000
Asset acquisitions, assets acquired and liabilities assumed, net						289,600
Asset acquisition, intangible assets acquired						11,600
Asset acquisition, intangible liabilities						$ 10,000
Asset acquisitions 2019 | Industrial property
Finite-Lived Intangible Assets [Line Items]
Number of properties acquired | property						17
Area of real estate property acquired | ft²						700,000
Asset acquisitions 2019 | Improved land parcels
Finite-Lived Intangible Assets [Line Items]
Number of properties acquired | property						4
Area of real estate property acquired | a						22.6
Asset acquisitions 2019 | Land
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions						$ 224,100
Asset acquisitions 2019 | Building
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions						$ 53,900