Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2019	Nov. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Summary Of Significant Accounting Policies [Line Items]
Non-controlling interests				$ 355,000
Operating lease liabilities	$ 5,545,000
Accounting Standards Update 2016-02 [Member]
Summary Of Significant Accounting Policies [Line Items]
Operating lease liabilities			$ 5,200,000
Operating lease and embedded financing lease right of use assets			$ 6,100,000
Spero Gyrase, Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Repurchase ownership percentage	100.00%	100.00%
Repurchase price per share	$ 0.001	$ 0.001
Non-controlling interests	$ 0			$ 400,000
Spero Potentiator Australia Pty Limited [Member] | Research and Development Expenses [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of refundable tax incentive	43.50%