Real Estate Investments - Dispositions (Details) - Real Estate Dispositions $ in Millions					3 Months Ended
	Mar. 31, 2017 USD ($) ft²	Mar. 30, 2017 USD ($) ft²	Mar. 07, 2017 USD ($) ft²	Mar. 06, 2017 USD ($) ft²	Mar. 31, 2017 USD ($) ft²
Real Estate Dispositions [Line Items]
Sales price	$ 82.0				$ 82.0
Closing Adjustments	(2.3)				(2.3)
Net proceeds					79.7
Net Real Estate Investment	50.8				50.8
Other (including receivables)(3)	$ 5.5				5.5
Gain					$ 23.4
Square footage | ft²	229,369				229,369
INDIANA
Real Estate Dispositions [Line Items]
Date Disposed				Mar. 06, 2017
Sales price				$ 6.4
Closing Adjustments				0.0
Net proceeds				6.4
Net Real Estate Investment				1.1
Other (including receivables)(3)				0.0
Gain				$ 5.3
Square footage | ft²				29,500
GEORGIA
Real Estate Dispositions [Line Items]
Date Disposed			Mar. 07, 2017
Sales price			$ 0.6
Closing Adjustments			0.0
Net proceeds			0.6
Net Real Estate Investment			0.6
Other (including receivables)(3)			0.0
Gain			$ 0.0
Square footage | ft²			12,000
NEVADA
Real Estate Dispositions [Line Items]
Date Disposed		Mar. 30, 2017
Sales price		$ 5.5
Closing Adjustments		(0.7)
Net proceeds		4.8
Net Real Estate Investment		2.2
Other (including receivables)(3)		0.3
Gain		$ 2.3
Square footage | ft²		18,147
TEXAS
Real Estate Dispositions [Line Items]
Date Disposed	Mar. 31, 2017
Sales price	$ 69.5				$ 69.5
Closing Adjustments	(1.6)				(1.6)
Net proceeds	67.9
Net Real Estate Investment	46.9				46.9
Other (including receivables)(3)	5.2				$ 5.2
Gain	$ 15.8
Square footage | ft²	169,722				169,722