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v3.20.2

Condensed Statements of Stockholders' Equity (Parenthetical) (Unaudited) - USD ($) $ in Thousands | 3 Months Ended
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Sep. 30, 2020 | Jun. 30, 2020
Common stock, issuance costs |  | $ 6,626
ATM |  |
Common stock, issuance costs | $ 561 |

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- Definition Common stock issuance costs. + References No definition available. + Details
Name: | stro_CommonStockIssuanceCosts
Namespace Prefix: | stro_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
Name: | us-gaap_SubsidiarySaleOfStockAxis=stro_AttheMarketIssuanceSalesAgreementMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |