Lease Intangibles - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Finite-Lived Intangible Assets [Line Items]
Below market rents, acquired		$ 7.9
Below market rents acquired, weighted average useful life		20 years 6 months
In-place lease intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired	$ 2.9	$ 24.2
Acquired intangible assets, weighted average useful life	8 years 1 month 6 days	5 years 2 months 12 days
Above-market rent
Finite-Lived Intangible Assets [Line Items]
Intangible assets acquired		$ 2.5
Acquired intangible assets, weighted average useful life		5 years 1 month 6 days