Related Person Transactions (Details) - Two North Riverside Plaza Joint Venture Limited Partnership	12 Months Ended
Dec. 31, 2020 USD ($) option	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Related Party Transaction [Line Items]
Lease term	5 years
Tenant improvements	$ 700,000
Renewal term of lease arrangement	1 year
Number of renewal options of lease arrangement \| option	0
Lessee, Operating Lease, Liability, Payment, Due [Abstract]
2021	$ 300,000
Operating lease, expense	900,000	$ 900,000	$ 800,000
Due to related party	$ 0	$ 0

Lessee, Operating Lease, Number Of Renewals

No definition available.

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- Definition

Amount for accounts payable to related parties.

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
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- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

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- Definition

Amount of operating lease expense. Excludes sublease income.

+ References

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- References

No definition available.

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Carrying amount as of the balance sheet date of improvements having a life longer than one year that were made for the benefit of one or more tenants.

+ References

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