The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

Commitments and Contingencies - DownREIT LLCs (Details) - property	Dec. 31, 2021	Dec. 31, 2020
Life Science JV \| Massachusetts
Loss Contingencies [Line Items]
Investment ownership percentage		49.00%
Indemnification Agreement
Loss Contingencies [Line Items]
Number of properties may be contributed in the agreement	29