Acquired Lease Intangibles - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Acquired Finite-Lived Intangible Assets
Amortization of below market lease liabilities	$ 1.8	$ 1.8	$ 0.1
In-place lease assets
Acquired Finite-Lived Intangible Assets
Amortization of lease assets	$ 9.7	10.2	2.9
Weighted-average remaining lives of lease assets	4 years 11 months 8 days
Below-market ground lease assets
Acquired Finite-Lived Intangible Assets
Amortization of lease assets	$ 0.1	0.1	0.1
Weighted-average remaining lives of lease assets	31 years 6 months 9 days
Above-market lease assets
Acquired Finite-Lived Intangible Assets
Amortization of lease assets	$ 0.8	$ 0.9	$ 0.3
Weighted-average remaining lives of lease assets	6 years 10 days
Below Market Lease
Acquired Finite-Lived Intangible Assets
Weighted-average remaining lives of lease liabilities	4 years 10 months 16 days
Below Market Lease Renewal Options
Acquired Finite-Lived Intangible Assets
Weighted-average remaining lives of lease assets	13 years 10 months 5 days