Leases - Narrative (Details) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) renewal lease	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Lease income	$ 378.3	$ 314.1	$ 291.4
Number of ground leases classified as operating | lease	5
Number of ground leases classified as financing | lease	2
Options to renew | renewal	0
Weighted-average remaining lease term in years	73 years 8 months 12 days	80 years 1 month 6 days
Operating lease cost	$ 3.7	$ 3.7
Operating lease payments	$ 1.6	$ 1.6
Chicago Illinois Office
Lessee, Lease, Description [Line Items]
Options to renew | renewal	0
Weighted-average remaining lease term in years	4 years