The Company and Basis of Presentation - Narrative (Details) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended	9 Months Ended
	Sep. 08, 2023	Jun. 26, 2023 USD ($) shares	Jun. 22, 2023 $ / shares shares	Apr. 30, 2023 employee	Jun. 30, 2023	Sep. 30, 2023 USD ($) segment $ / shares	Dec. 31, 2022 USD ($) $ / shares
Company and Basis of Presentation [Line Items]
Number of operating segments | segment						1
Employee workforce, termination percentage				83.00%	83.00%
Preferred stock, par value (in dollars per share) | $ / shares						$ 0.0001	$ 0.0001
Accumulated deficit | $						$ 701,234	$ 425,624
Cash, cash equivalents, and marketable securities | $						$ 203,600
Number of employees retained | employee				10
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]
Conversion basis			40
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			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			364,887
Private Placement | Series A Non Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Number of shares sold in private placement		721,452
Gross proceeds received in private placement | $		$ 210,000
Placement agent and other offering expenses in private placement | $		$ 12,700
Common Stock
Company and Basis of Presentation [Line Items]
Reverse stock split, conversion ratio	0.04
Common Stock | Asset Acquisition
Company and Basis of Presentation [Line Items]
Number of shares transferred as equity interest in asset acquisition			517,809