Intangibles - (Details)	12 Months Ended
	Dec. 31, 2017 USD ($)
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible items, net income impact	$ (1,500,000)
Weighted average amortization period for lease intangibles	18 years
Weighted average amortization period for lease intangible liability	20 years
In-place leases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, disposals	$ 3,500,000
Impairment of intangible assets, accumulated amortization	2,100,000
Impairment of intangible assets	(1,400,000)
Above-market leases
Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, disposals	300,000
Impairment of intangible assets, accumulated amortization	100,000
Impairment of intangible assets	(200,000)
Below-market lease
Finite-Lived Intangible Assets [Line Items]
Impairment of intangible assets	100,000
Impairment of intangible liabilities, finite-lived	100,000
Impairment of intangible liabilities, finite-lived, accumulated accretion	$ 36,000.0