Amount of revenue, fees and commissions earned from transactions between (a) a parent company and its subsidiaries; (b) subsidiaries of a common parent; (c) an entity and trusts for the benefit of employees, for example, but not limited to, pension and profit-sharing trusts that are managed by or under the trusteeship of the entity's management; (d) an entity and its principal, owners, management, or members of their immediate families; and (e) affiliates.

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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Publisher FASB
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Name:	us-gaap_RevenueFromRelatedParties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Related Party Transactions (Details) $ in Millions	3 Months Ended		6 Months Ended
Related Party Transactions (Details) $ in Millions	Jun. 30, 2021 USD ($) ft² property	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) ft² property	Jun. 30, 2020 USD ($)
Related Party Transaction [Line Items]
Area of real estate property (in square feet) \| ft²	10,100,000		10,100,000
Affliliated entity \| Supervisory fee revenue
Related Party Transaction [Line Items]
Revenue from related parties	$ 0.3	$ 0.2	$ 0.5	$ 0.5
Affliliated entity \| Property management fee revenue
Related Party Transaction [Line Items]
Revenue from related parties	0.1	0.1	0.1	0.2
Affliliated entity \| Leased space rental
Related Party Transaction [Line Items]
Revenue from related parties	$ 0.1	$ 0.1	$ 0.2	$ 0.2
Number of properties \| property	1		1
Lease cancellation, notice period (in days)			90 days
Undivided Interest
Related Party Transaction [Line Items]
Area of real estate property (in square feet) \| ft²	5,447		5,447
Chairman emeritus \| Leased space rental
Related Party Transaction [Line Items]
Percentage of lease space occupied by Chairman emeritus and employee			15.00%