Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Accounting Policies [Abstract]
Charge for uncollectible amounts	$ 0.8	$ 29.8	$ 2.5	$ 35.0
Office parking revenue	16.2	$ 14.7	31.1	$ 44.9
Office parking receivables	$ 0.7		$ 0.7		$ 0.6