Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair value, assets, level 1 to level 2 transfers, amount	$ 0	$ 0
Fair value, assets, level 2 to level 1 transfers, amount	0	0
Fair value, assets, level 3 to level 1 transfers, amount	0	0
Fair value, assets, level 1 to level 3 transfers, amount	$ 0	$ 0

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 3.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Amount of transfers of assets measured on a recurring basis out of Level 3 of the fair value hierarchy into Level 1.

+ References

No definition available.

+ Details

Name:	sldb_FairValueAssetsLevel3toLevel1TransfersAmount
Namespace Prefix:	sldb_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of transfers of assets measured on a recurring basis out of Level 1 of the fair value hierarchy into Level 2.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bb)
-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	credit
Period Type:	instant

- Definition

Amount of transfers of assets measured on a recurring basis out of Level 2 of the fair value hierarchy into Level 1.

+ References

+ Details

Name:	us-gaap_FairValueAssetsLevel2ToLevel1TransfersAmount
Namespace Prefix:	us-gaap_
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Period Type:	instant

- References

No definition available.

+ Details

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