Cover - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Feb. 21, 2024	Jun. 30, 2023
Cover [Abstract]
Document Type	10-K/A
Document Annual Report	true
Document Period End Date	Dec. 31, 2023
Current Fiscal Year End Date	--12-31
Document Transition Report	false
Entity File Number	001-37722
Entity Registrant Name	SPYRE THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	46-4312787
Entity Address, Address Line One	221 Crescent Street
Entity Address, Address Line Two	Building 23, Suite 105
Entity Address, City or Town	Waltham
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02453
City Area Code	617
Local Phone Number	651-5940
Title of 12(b) Security	Common Stock, $0.0001 Par Value Per Share
Trading Symbol	SYRE
Security Exchange Name	NASDAQ
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction	true
Document Financial Statement Restatement Recovery Analysis [Flag]	true
Entity Shell Company	false
Entity Public Float			$ 26.2
Entity Common Stock Shares Outstanding		36,150,941
Entity Central Index Key	0001636282
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	FY
Amendment Flag	true
Amendment Description	This Amendment No. 2 on Form 10-K/A (this “Amendment”) amends the Annual Report on Form 10-K of Spyre Therapeutics, Inc. (the “Company”) for the fiscal year ended December 31, 2023, as filed with the Securities and Exchange Commission on February 29, 2024, as amended by Form 10-K/A of the Company filed with the Securities and Exchange Commission on March 1, 2024 (as amended, the "Original Filing").Subsequent to the filing of its Form 10-Q for the three and nine months ended September 30, 2024, the Company became aware of a misapplication of Generally Accepted Accounting Principles in the United States ("U.S. GAAP") as it relates to the Company's exclusion of its Series A non-voting convertible preferred stock and Series B non-voting convertible preferred stock in the calculation of basic and diluted net loss per share and a finding of a material weakness in internal control over financial reporting solely related to such matter. This Amendment is being filed for the sole purpose of amending certain disclosures from the Original Filing related to the aforementioned misapplication of U.S. GAAP and related finding of material weakness in internal control over financial reporting.Specifically, this Amendment amends: (i) Part II, Item 8. "Financial Statements and Supplementary Data" to update the Company's Consolidated Statement of Operations and related footnote disclosures for the twelve months ended December 31, 2023, (ii) Part II, Item 9A. "Controls and Procedures" to address management's re-evaluation of disclosure controls and procedures as of December 31, 2023 and to reflect the identification of a material weakness in our internal control over financial reporting and (iii) Part IV, Item 15. "Exhibits and Financial Statement Schedules" to include, in accordance with Rule 12b-15 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), updated certifications from our Chief Executive Officer and Chief Financial Officer as required by Sections 302 and 906 of the Sarbanes-Oxley Act of 2002 as Exhibits 31.1, 31.2 and 32.1 and an updated Consent of Independent Registered Public Accounting Firm as Exhibit 23.1. In accordance with Rule 12b-15 under the Exchange Act, this Amendment amends and restates in their entirety each item identified in the paragraph above.Other than as described above, this Amendment does not amend, update or change any other items or disclosures contained in the Original Filing, and accordingly, all other information contained in this Amendment is as of the date of the original filing and does not reflect subsequent information or events beyond the original filing date, February 29, 2024. Accordingly, this Amendment should be read in conjunction with other filings made with the SEC subsequent to the filing of the Original Filing, including any amendments to those filings. Capitalized terms used but not defined herein shall have the meanings ascribed to such terms in the Original Filing.