Real Estate Investments - Dispositions (Details) $ in Millions				1 Months Ended	3 Months Ended	9 Months Ended
	Aug. 28, 2019 USD ($)	Aug. 01, 2019 USD ($) ft²	Apr. 09, 2019 USD ($) ft²	May 31, 2019 USD ($)	Jun. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) ft²	Oct. 25, 2019 USD ($) ft²
Real Estate Dispositions [Line Items]
Sales price						$ 15.2
Closing Adjustments						(1.1)
Net Proceeds						14.1
Net Real Estate Investment						8.7
Real Estate Other						0.4
Gain/(Impairment)						$ 5.0
Square footage | ft²						87,483
Erie, Pennsylvania
Real Estate Dispositions [Line Items]
Impairment of assets held-for-sale				$ 5.2
Real Estate Dispositions | Erie, Pennsylvania
Real Estate Dispositions [Line Items]
Purchase price						$ 1.3
Net investment						$ 14.0
Real Estate Dispositions | Tucson, AZ (3)
Real Estate Dispositions [Line Items]
Disposal Date			Apr. 09, 2019
Sales price			$ 13.0
Closing Adjustments			(0.9)
Net Proceeds			12.1
Net Real Estate Investment			6.9
Real Estate Other			0.4
Gain/(Impairment)			$ 4.8
Square footage | ft²			67,345
Real Estate Dispositions | Virginia Beach, VA (4)
Real Estate Dispositions [Line Items]
Impairment of assets held-for-sale					$ 0.4
Disposal Date		Aug. 01, 2019
Sales price		$ 1.3
Closing Adjustments		(0.1)
Net Proceeds		1.2
Net Real Estate Investment		1.2
Real Estate Other		0.0
Gain/(Impairment)		$ 0.0
Square footage | ft²		10,000
Real Estate Dispositions | San Antonio, TX
Real Estate Dispositions [Line Items]
Disposal Date	Aug. 28, 2019
Sales price			$ 0.9
Closing Adjustments			(0.1)
Net Proceeds	$ 0.8
Net Real Estate Investment			0.6
Real Estate Other			$ 0.0
Gain/(Impairment)	$ 0.2
Square footage | ft²			10,138
Subsequent Event | Real Estate Dispositions | Erie, Pennsylvania
Real Estate Dispositions [Line Items]
Sales price							$ 14.0
Net Real Estate Investment							$ 1.3
Square footage | ft²							90,123