The Company and Basis of Presentation (Details) $ / shares in Units, $ in Thousands										1 Months Ended		3 Months Ended			9 Months Ended	115 Months Ended
	May 14, 2024 shares	Apr. 23, 2024 shares	Mar. 20, 2024 USD ($) shares	Mar. 18, 2024 shares	Dec. 11, 2023 USD ($) $ / shares shares	Nov. 21, 2023 shares	Sep. 08, 2023	Jun. 26, 2023 USD ($) shares	Jun. 22, 2023 $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares	Apr. 30, 2023	Jun. 30, 2024 shares	Mar. 31, 2024 shares	Jun. 30, 2023 shares	Sep. 30, 2024 USD ($) segment $ / shares shares	Sep. 30, 2024 USD ($) $ / shares shares	Sep. 06, 2024 USD ($)	Apr. 25, 2024 shares	Apr. 24, 2024 shares	Dec. 31, 2023 USD ($) $ / shares shares	Nov. 22, 2023 shares
Company and Basis of Presentation [Line Items]
Number of operating segments | segment															1
Employee workforce, termination percentage											83.00%			83.00%
Common stock, par value (in dollars per share) | $ / shares										$ 0.0001					$ 0.0001	$ 0.0001				$ 0.0001
Series B non-voting convertible preferred stock, par value (in dollars per share) | $ / shares					$ 0.0001
Proceeds from raising capital | $																$ 1,100,000
Accumulated deficit | $										$ 916,136					$ 916,136	916,136				$ 764,414
Marketable securities | $										$ 414,200					$ 414,200	$ 414,200
Asset Acquisition
Company and Basis of Presentation [Line Items]
Fixed exchange ratio									54.94488%
Spyre Therapeutics, Inc.
Company and Basis of Presentation [Line Items]
Asset acquisition, stockholder payment period									3 years
Asset acquisition, cash payment, threshold period									1 year
Spyre 2023 Equity Incentive Plan | Asset Acquisition
Company and Basis of Presentation [Line Items]
Number of outstanding and unexercised stock options to purchase (in shares)									2,734
Spyre 2023 Equity Incentive Plan | Spyre Therapeutics, Inc.
Company and Basis of Presentation [Line Items]
Number of outstanding and unexercised stock options to purchase (in shares)									2,734
Series A Non Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares										$ 0.0001					$ 0.0001	$ 0.0001				$ 0.0001
Conversion basis									40
Preferred stock, not automatically converted, outstanding (in shares)																					437,037
Issuance of non-voting convertible preferred stock (in shares)								721,452
Exchange of Series A non-voting convertible preferred stock into common stock (in shares)		90,992
Preferred stock, outstanding (in shares)										346,045					346,045	346,045		346,045	346,045	437,037
Series A Non Voting Convertible Preferred Stock | Asset Acquisition
Company and Basis of Presentation [Line Items]
Number of shares transferred as equity interest in asset acquisition (in shares)									364,887
Preferred stock, par value (in dollars per share) | $ / shares									$ 0.0001
Conversion basis									40
Series A Non Voting Convertible Preferred Stock | Spyre Therapeutics, Inc.
Company and Basis of Presentation [Line Items]
Number of shares transferred as equity interest in asset acquisition (in shares)									364,887
Series B Non Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Preferred stock, par value (in dollars per share) | $ / shares										$ 0.0001					$ 0.0001	$ 0.0001
Conversion basis			40
Preferred stock, not automatically converted, outstanding (in shares)										16,667					16,667	16,667
Series B non-voting convertible preferred stock, par value (in dollars per share) | $ / shares																				$ 0.0001
Issuance of non-voting convertible preferred stock (in shares)			121,625	271,625	150,000
Preferred stock, outstanding (in shares)										16,667					16,667	16,667
Common Stock
Company and Basis of Presentation [Line Items]
Exchange of Series A non-voting convertible preferred stock into common stock (in shares)		3,639,680
Private Placement
Company and Basis of Presentation [Line Items]
Gross proceeds received in private placement | $					$ 180,000
Placement agent and other offering costs | $			$ 11,200		10,900
Private Placement | Series A Non Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Number of shares sold in private placement (in shares)								721,452
Gross proceeds received in private placement | $								$ 210,000
Placement agent and other offering expenses in private placement | $								$ 12,700
Private Placement | Series B Non Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Gross proceeds received in private placement | $			$ 180,000		$ 90,000
At-The-Market Offering
Company and Basis of Presentation [Line Items]
Sale of stock, authorized amount | $																	$ 500,000
At-The-Market Offering | Common Stock
Company and Basis of Presentation [Line Items]
Number of shares of common stock sold (in shares)										426,287
Sale of stock, aggregate offering price | $																	$ 200,000
Sale of stock, price per share (in dollars per share) | $ / shares										$ 28.15					$ 28.15	$ 28.15
Sale of stock, proceeds received | $										$ 11,800
Common Stock
Company and Basis of Presentation [Line Items]
Reverse stock split, conversion ratio							0.04
Shares converted (in shares)												10,198,000
Exchange of Series A non-voting convertible preferred stock into common stock (in shares)												3,640,000
Common Stock | Conversion Of Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Shares converted (in shares)						25,972,080
Common Stock | Conversion Of Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Shares converted (in shares)	10,198,320														10,198,320
Common Stock | Asset Acquisition
Company and Basis of Presentation [Line Items]
Number of shares transferred as equity interest in asset acquisition (in shares)									517,809
Common stock, par value (in dollars per share) | $ / shares									$ 0.0001
Common Stock | Private Placement
Company and Basis of Presentation [Line Items]
Number of shares of common stock sold (in shares)					6,000,000
Preferred Stock | Series A Non Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Issuance of non-voting convertible preferred stock (in shares)														721,000
Exchange of Series A non-voting convertible preferred stock into common stock (in shares)												(91,000)
Preferred stock, outstanding (in shares)										346,000		346,000	437,000		346,000	346,000				437,000
Preferred Stock | Series A Non Voting Convertible Preferred Stock | Conversion Of Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Shares converted (in shares)						649,302
Preferred Stock | Series B Non Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Shares converted (in shares)												(255,000)
Issuance of non-voting convertible preferred stock (in shares)													122,000
Preferred stock, outstanding (in shares)										17,000		17,000	0		17,000	17,000				0
Preferred Stock | Series B Non Voting Convertible Preferred Stock | Conversion Of Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Shares converted (in shares)	254,958														254,958