The Company and Basis of Presentation (Details) $ / shares in Units, $ in Thousands											1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 29, 2024 USD ($) $ / shares shares	Nov. 20, 2024 shares	May 14, 2024 shares	Apr. 23, 2024 shares	Mar. 20, 2024 USD ($) $ / shares shares	Mar. 18, 2024 shares	Dec. 11, 2023 USD ($) $ / shares shares	Sep. 08, 2023	Jun. 26, 2023 USD ($) $ / shares shares	Jun. 22, 2023 $ / shares shares	Jun. 30, 2023 shares	Jun. 30, 2023	Dec. 31, 2024 USD ($) segment $ / shares shares	Dec. 31, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) shares	Sep. 06, 2024 USD ($)	Apr. 25, 2024 shares	Dec. 08, 2023	May 31, 2022 $ / shares	Dec. 31, 2021 shares
Company and Basis of Presentation [Line Items]
Number of operating segments | segment													1
Employee workforce, termination percentage												83.00%
Convertible preferred stock, par value (in dollars per share) | $ / shares													$ 0.0001
Series B non-voting convertible preferred stock, par value (in dollars per share) | $ / shares														$ 0.0001
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)							150,000						122,000	150,000
Proceeds from raising capital | $													$ 1,300,000
Accumulated deficit | $													(972,432)	$ (764,414)
Cash, cash equivalents, and marketable securities | $													603,100
Private Placement
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)									721,452		721,452
Proceeds from issuance of private placement, net | $													$ 180,000
Offering costs | $					$ 11,200		$ 5,400		$ 12,700
Public offering price (in dollars per share) | $ / shares									$ 291.08
Aggregate purchase price for stock sold | $					$ 168,900		$ 84,600		$ 197,300
At-The-Market Offering
Company and Basis of Presentation [Line Items]
Sale of stock, authorized amount | $																$ 500,000
Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Convertible preferred stock, par value (in dollars per share) | $ / shares													$ 0.0001	$ 0.0001
Conversion basis										40
Proceeds from issuance of private placement, net | $													$ 0	$ 197,364	$ 0
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)				90,992
Preferred stock, outstanding (in shares)													346,045	437,037			346,045
Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Convertible preferred stock, par value (in dollars per share) | $ / shares													$ 0.0001	$ 0.0001
Conversion basis					40		40											40
Proceeds from issuance of private placement, net | $													$ 168,850	$ 84,555	0
Series B non-voting convertible preferred stock, par value (in dollars per share) | $ / shares							$ 0.0001
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)					121,625	271,625	150,000
Preferred stock, outstanding (in shares)													16,667	16,667
Preferred stock, not automatically converted, outstanding (in shares)													16,667
Series B Non-Voting Convertible Preferred Stock | Private Placement
Company and Basis of Presentation [Line Items]
Offering costs | $							$ 10,900
Issuance of Series B non-voting convertible preferred stock in connection with private placement, net of financing costs (in shares)					121,625	271,625	150,000
Public offering price (in dollars per share) | $ / shares					$ 1,480		$ 600
Aggregate purchase price for stock sold | $							$ 169,100
Common Stock
Company and Basis of Presentation [Line Items]
Proceeds from issuance of private placement, net | $													$ 0	$ 84,555	$ 0
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)				3,639,680
Common Stock | At-The-Market Offering
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)													777,432
Offering costs | $													$ 400
Sale of stock, aggregate offering price | $																$ 200,000
Public offering price (in dollars per share) | $ / shares													$ 26.935
Aggregate purchase price for stock sold | $													$ 20,500
Common Stock | Underwritten Offering
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)		8,366,250
Offering costs | $	$ 14,200
Public offering price (in dollars per share) | $ / shares	$ 27.50
Aggregate purchase price for stock sold | $	$ 215,900
Common Stock | Over-Allotment Option
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)	1,091,250
Common Stock
Company and Basis of Presentation [Line Items]
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)													3,640,000
Public offering price (in dollars per share) | $ / shares																			$ 40.00
Reverse stock split, conversion ratio								0.04
Common Stock | Conversion Of Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)			10,198,320										10,198,320
Common Stock | Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)														25,972,000
Common Stock | Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Conversion of non-voting convertible preferred stock into common stock (in shares)													10,198,000
Common Stock | Series B Non-Voting Convertible Preferred Stock | Private Placement
Company and Basis of Presentation [Line Items]
Sale of stock (in shares)							6,000,000
Public offering price (in dollars per share) | $ / shares							$ 15.00
Preferred Stock | Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Exchange of Series A non-voting convertible preferred stock for common stock (in shares)													(91,000)
Preferred stock, outstanding (in shares)													346,000	437,000	0					0
Conversion of non-voting convertible preferred stock into common stock (in shares)														(649,000)
Preferred Stock | Series B Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Preferred stock, outstanding (in shares)													17,000	0	0					0
Conversion of non-voting convertible preferred stock into common stock (in shares)													(255,000)
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]
Conversion of non-voting convertible preferred stock into common stock (in shares)			254,958										254,958
Spyre Therapeutics, Inc.
Company and Basis of Presentation [Line Items]
Fixed exchange ratio										0.5494488
Asset acquisition, stockholder payment period										3 years
Asset acquisition, cash payment, threshold period										1 year
Spyre Therapeutics, Inc. | Spyre 2023 Equity Incentive Plan
Company and Basis of Presentation [Line Items]
Number of outstanding and unexercised stock options to purchase (in shares)										2,734
Spyre Therapeutics, Inc. | Series A Non-Voting Convertible Preferred Stock
Company and Basis of Presentation [Line Items]
Shares transferred as equity interest in asset acquisition (in shares)										364,887
Convertible preferred stock, par value (in dollars per share) | $ / shares										$ 0.0001
Conversion basis										40
Spyre Therapeutics, Inc. | Common Stock
Company and Basis of Presentation [Line Items]
Shares transferred as equity interest in asset acquisition (in shares)										517,809