Significant Accounting Polices - Additional Information (Details) - USD ($)			3 Months Ended
	Mar. 19, 2021	Jan. 25, 2021	Mar. 31, 2021	Mar. 31, 2020	Apr. 30, 2021	Dec. 31, 2020
Schedule Of Significant Accounting Policies [Line Items]
Upfront nonrefundable payment		$ 1,000,000.0
Loan in principal amount		$ 4,000,000.0
Issuance and bore interest rate		6.00%
Reimbursement payment	$ 14,000,000.0
Collaboration agreement amount	25,000,000.0
Development payments	10,000,000.0
Deferred collaboration funding, short-term			$ 19,016,258
Deferred collaboration funding, long-term			4,800,000
Accounts receivable			$ 10,000,000
Accounting Standards Update [Extensible List]			acer:AccountingStandardsUpdate202006Member
Change in accounting principle, accounting standards update, adopted			true
Change in accounting principle, accounting standards update, adoption date			Mar. 31, 2021
Change in accounting principle, accounting standards update, immaterial effect			true
Income tax expense (benefit)			$ 0	$ 0
Cash and Cash Equivalents
Schedule Of Significant Accounting Policies [Line Items]
Investments in money market funds			15,400,000			$ 5,300,000
First Development Payment
Schedule Of Significant Accounting Policies [Line Items]
Collaboration agreement amount			10,000,000.0
First Development Payment | Subsequent Event
Schedule Of Significant Accounting Policies [Line Items]
Collaboration agreement amount					$ 5,000,000.0
Performance Obligations
Schedule Of Significant Accounting Policies [Line Items]
Deferred collaboration funding, short-term and long-term			23,800,000
Deferred collaboration funding, short-term			19,000,000.0
Deferred collaboration funding, long-term			4,800,000
Deferred collaboration funding, cash received			15,000,000.0
Accounts receivable			10,000,000.0
Revenue recognized			900,000
Offset to research and development expense			300,000
Relief
Schedule Of Significant Accounting Policies [Line Items]
Non-cash reduction recognized in secured loan			4,000,000.0
Collaboration Agreement | Relief
Schedule Of Significant Accounting Policies [Line Items]
Cash payment received	10,000,000.0	$ 10,000,000.0
Reimbursement payment	14,000,000.0	14,000,000.0
Repayment of outstanding balance of prior loan and interest	4,000,000.0	4,000,000.0
Development and commercial launch costs	20,000,000.0
Development payments subject new drug application		$ 10,000,000.0	$ 10,000,000.0
Development payments subject to new drug application, Installment amount	$ 5,000,000.0
Net profit split ratio based on territory	60.00%	60.00%
Percentage of royalty revenue received	15.00%	15.00%
Milestone payment to be received	$ 6,000,000.0	$ 6,000,000.0
Percentage of development and commercialization services	60.00%
Percentage of payment net profit territory	60.00%
Upfront non-refundable payment received		$ 1,000,000.0
Collaboration Agreement | Relief | First Development Payment
Schedule Of Significant Accounting Policies [Line Items]
Development payments subject new drug application	$ 10,000,000.0
Collaboration Agreement | Relief | Second Development Payment
Schedule Of Significant Accounting Policies [Line Items]
Development payments subject new drug application	10,000,000.0
Collaboration And License Agreement
Schedule Of Significant Accounting Policies [Line Items]
Upfront non-refundable payment received	$ 1,000,000.0