Summary of Significant Accounting Policies - Antidilutive Shares (Details) - shares	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020
Antidilutive Securities
Anti-dilutive shares	7,448,581	6,339,120
Unvested restricted incentive shares and units
Antidilutive Securities
Anti-dilutive shares	1,105,300	589,276
Share options
Antidilutive Securities
Anti-dilutive shares	6,343,281	5,749,844

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=124432515&loc=d3e3550-109257

Name:	us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration