Investments in Real Estate - Narrative (Details) ft² in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020 USD ($) ft² property	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($) ft² a property	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2020 USD ($) property	Sep. 30, 2020 property	Sep. 30, 2020 ft² property	Sep. 30, 2020 a property	Sep. 30, 2019 USD ($) ft² a property	Sep. 30, 2020 ft²	Sep. 30, 2020 a
Finite-Lived Intangible Assets [Line Items]
Rental revenues and tenant expense reimbursements	$ 47,147			$ 43,397			$ 138,005				$ 126,007
Net income	22,722	$ 30,704	$ 12,856	14,784	$ 10,379	$ 15,532	66,282				40,695
Capitalized interest associated with redevelopment activities	$ (400)			(900)			$ (1,500)				(2,500)
Improved land parcels
Finite-Lived Intangible Assets [Line Items]
Number of properties | property	22						22	22	22	22
Square feet | ft²												13,100
Improved land parcels | Miami
Finite-Lived Intangible Assets [Line Items]
Number of properties | property	1						1	1	1	1
Redevelopment property
Finite-Lived Intangible Assets [Line Items]
Number of properties | property	1						1	1	1	1
Square feet												200	85.0
Asset acquisition, consideration transferred							$ 63,300
Asset acquisition, real estate development costs							61,200
Redevelopment property | Kent 192 | Seattle
Finite-Lived Intangible Assets [Line Items]
Square feet | ft²												200
Asset acquisition, real estate development costs							33,900
Asset Acquisitions 2020
Finite-Lived Intangible Assets [Line Items]
Purchase Price (in thousands)	$ 6,500						47,600
Finite-lived intangible assets acquired	500						1,800
Asset Acquisition, Intangible Liabilities	100						700
Rental revenues and tenant expense reimbursements	800						1,500
Net income	$ 400						700
Asset Acquisitions 2020 | Industrial building
Finite-Lived Intangible Assets [Line Items]
Number of properties acquired | property	1							3
Area of real estate property acquired	22								101	5.5
Asset Acquisitions 2020 | Improved land parcels
Finite-Lived Intangible Assets [Line Items]
Number of properties acquired | property								2
Asset Acquisitions 2020 | Land
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions	$ 3,700						34,800
Asset Acquisitions 2020 | Building
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions	$ 2,300						$ 11,000
Asset Acquisitions 2019
Finite-Lived Intangible Assets [Line Items]
Purchase Price (in thousands)				148,300							267,700
Finite-lived intangible assets acquired				4,300							11,500
Asset Acquisition, Intangible Liabilities				3,500							9,900
Rental revenues and tenant expense reimbursements				2,400							3,800
Net income				$ 900							$ 1,600
Asset Acquisitions 2019 | Industrial building
Finite-Lived Intangible Assets [Line Items]
Number of properties acquired | property				11							15
Area of real estate property acquired | ft²				442							608
Asset Acquisitions 2019 | Improved land parcels
Finite-Lived Intangible Assets [Line Items]
Number of properties acquired | property				1							3
Area of real estate property acquired | a				2.0							21.7
Asset Acquisitions 2019 | Land
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions				$ 118,600							$ 213,000
Asset Acquisitions 2019 | Building
Finite-Lived Intangible Assets [Line Items]
Asset acquisition, property additions				$ 25,400							$ 43,200