Intangibles - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Intangibles
Net recognition of loss in rental income from intangible amortization write offs	$ (0.3)	$ (1.3)
Weighted average amortization period for lease intangibles		17 years
Weighted average amortization period for lease intangible liability		20 years
In-place lease intangible
Intangibles
Finite-lived intangible assets, disposals	0.4	$ 3.1
Above market lease intangible accumulated amortization written off	$ 0.1	$ 1.9