Noncontrolling Interest - Common Shares and Units Activity (Details) - shares	9 Months Ended
Sep. 30, 2021
Equity Commonwealth
Increase (Decrease) in Stockholders' Equity
Ownership percentage by noncontrolling owners	0.20%
Common Shares
Increase (Decrease) in Stockholders' Equity
Balance as of beginning of period (in shares)	121,522,555
Repurchase of shares (in shares)	(676,086)
Share-based compensation grants and vesting, net of forfeitures (in shares)	664,633
Balance as of end of period (in shares)	121,511,102
OP Units and LTIP Units \| Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity
Balance as of beginning of period (in shares)	243,516
Repurchase of shares (in shares)	0
Share-based compensation grants and vesting, net of forfeitures (in shares)	3,701
Balance as of end of period (in shares)	247,217
Common Stock, OP Units, and LTIP Units
Increase (Decrease) in Stockholders' Equity
Balance as of beginning of period (in shares)	121,766,071
Repurchase of shares (in shares)	(676,086)
Share-based compensation grants and vesting, net of forfeitures (in shares)	668,334
Balance as of end of period (in shares)	121,758,319

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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- Definition

Number of shares issued which are neither cancelled nor held in the treasury.

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- Definition

Number, after forfeiture, of shares or units issued under share-based payment arrangement. Excludes shares or units issued under employee stock ownership plan (ESOP).

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Number of shares that have been repurchased and retired during the period.

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