Leases - Schedule of right-of-use assets and lease liabilities related to ground leases (Details) - Ground - USD ($) $ in Millions	Mar. 31, 2020	Dec. 31, 2019
Assets:
Right-of-use assets, at fair value	$ 25.8	$ 25.7
Liabilities:
Ground lease liabilities, at fair value	$ 25.8	$ 25.7
Key Terms:
Weighted-average remaining lease term (years)	83 years 10 months 24 days	84 years 4 months 24 days
Weighted-average discount rate	6.16%	6.15%