Favorable and Unfavorable Acquired Lease Contracts, net - Favorable Lease Contracts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 7.2	$ 14.6	$ 15.1
Weighted average life (years)	10 years 10 months 24 days
Favorable
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 6.6	$ 8.3	$ 10.1
Weighted average life (years)	14 years 1 month 6 days	11 years 10 months 24 days	11 years 1 month 6 days