Collaboration and License Agreements - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021	Jul. 31, 2020
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenues						$ 7,800,000
Acceleron Collaboration Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non refundable upfront payment received		$ 10,000,000.0			$ 10,000,000.0
Range of tiered royalties on net sales					mid single-digit percentage to a low double-digit percentage
Change in variable consideration constrained			$ 0		$ 0
Revenues			0	$ 2,900,000	1,000,000.0
Deferred Revenue	$ 6,100,000			2,300,000		2,300,000	$ 600,000
Accounts Receivable, Related Parties			100,000		100,000		0
Deferred revenue current and non-current			0		0		600,000
Reimbursement Payment Received					4,900,000		3,900,000
Unbilled accounts receivable related to reimbursable research and development cost							700,000
Acceleron Collaboration Agreement | Research Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non refundable upfront payment received	2,000,000.0
Aggregate amount receivable on achievement of milestone			2,000,000.0		2,000,000.0
Amount received on achievement of milestone					2,000,000.0		2,000,000.0
Acceleron Collaboration Agreement | Research Milestones | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate amount receivable on achievement of milestone			18,500,000		18,500,000
Acceleron Collaboration Agreement | Clinical and Regulatory Milestones | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate amount receivable on achievement of milestone			202,500,000		202,500,000
Acceleron Collaboration Agreement | Worldwide Net Sales Milestones | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate amount receivable on achievement of milestone			217,500,000		217,500,000
MyoKardia Collaboration and License Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non refundable upfront payment received					10,000,000.0
Revenues			1,200,000	2,100,000	4,700,000	6,300,000
Deferred Revenue	$ 5,600		400,000	$ 1,500	400,000	$ 1,500	2,700,000
Accounts Receivable, Related Parties			0		0		2,500,000
Deferred revenue current and non-current			1,400,000		1,400,000		4,100,000
Reimbursement Payment Received					4,800,000		3,200,000
Unbilled accounts receivable related to reimbursable research and development cost			800,000		800,000		500,000
Upfront payment								$ 10,000,000.0
Payment for prepaid research funding			2,500,000		2,500,000			2,500,000
Prepaid research funding payment received			2,500,000		2,500,000
MyoKardia Collaboration and License Agreement | Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment for certain identified targets								298,500,000
Milestone payment for certain other identified targets								$ 150,000,000.0
MyoKardia Collaboration and License Agreement | Clinical and Regulatory Milestones
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Aggregate amount receivable on achievement of milestone			$ 2,500,000		$ 2,500,000		$ 2,500,000