Stock-Based Awards - Summary of Stock Option Activity (Details) - 2018 Stock Option and Incentive Plan $ / shares in Units, $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2023 USD ($) $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares
Number of Shares
Number of Shares, outstanding beginning balance (in shares) \| shares	8,233,330
Number of Shares, granted (in shares) \| shares	3,068,900
Number of Shares, exercised (in shares) \| shares	(13,401)
Number of Shares, forfeited (in shares) \| shares	(1,189,831)
Number of Shares, outstanding ending balance (in shares) \| shares	10,098,998	8,233,330
Number of Shares, options exercisable at ending balance (in shares) \| shares	6,305,828
Number of Shares, vested and expected to vest at ending balance (in shares) \| shares	10,098,998
Weighted Average Exercise Price
Weighted Average Exercise Price, Outstanding beginning balance (in dollars per share) \| $ / shares	$ 5.74
Weighted Average Exercise Price, Granted (in dollars per share) \| $ / shares	0.69
Weighted Average Exercise Price, Exercised (in dollars per share) \| $ / shares	0.35
Weighted Average Exercise Price, Forfeited (in dollars per share) \| $ / shares	2.65
Weighted Average Exercise Price, Outstanding ending balance (in dollars per share) \| $ / shares	4.58	$ 5.74
Weighted Average Exercise Price, Exercisable at ending balance (in dollars per share) \| $ / shares	5.78
Weighted Average Exercise Price, Vested and expected to vest at ending balance (in dollars per share) \| $ / shares	$ 4.58
Stock Option Activity, Additional Disclosures
Weighted Average Remaining Contractual Term (in years), Outstanding	6 years 11 months 12 days	6 years 8 months 4 days
Weighted Average Remaining Contractual Term (in years), Options exercisable	5 years 7 months 28 days
Weighted Average Remaining Contractual Term (in years), Vested and expected to vest	6 years 11 months 12 days
Aggregate Intrinsic Value (in dollars per share) \| $	$ 604	$ 159
Aggregate Intrinsic Value, Options exercisable at ending balance (in dollars per share) \| $	188
Aggregate Intrinsic Value, Vested and expected to vest at ending balance (In dollars per share) \| $	$ 604

Surface Oncology, Inc. 10-Q