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Summary of Significant Accounting Policies - Summary of Subsidiaries Not Wholly Owned (Detail) | 12 Months Ended
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Dec. 31, 2016
Spero Potentiator, Inc. [Member] | United States [Member] |
Summary Of Significant Accounting Policies [Line Items] |
Relationship | Controlling interest
Year of Inclusion | 2014
Spero Europe, Ltd. [Member] | United Kingdom [Member] |
Summary Of Significant Accounting Policies [Line Items] |
Relationship | Controlling interest
Year of Inclusion | 2015
Spero Gyrase, Inc. [Member] | United States [Member] |
Summary Of Significant Accounting Policies [Line Items] |
Relationship | Controlling interest
Year of Inclusion | 2016
Spero Cantab, Inc. [Member] | United States [Member] |
Summary Of Significant Accounting Policies [Line Items] |
Relationship | Controlling interest
Year of Inclusion | 2016

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