Common Stock and Preferred Stock - Narrative (Details) $ / shares in Units, $ in Millions			3 Months Ended
	Nov. 04, 2021 USD ($)	Dec. 17, 2019 USD ($)	Mar. 31, 2021 USD ($) $ / shares shares	Dec. 31, 2022 vote shares	Dec. 31, 2021 shares
Subsidiary, Sale of Stock [Line Items]
Common stock, shares authorized (in shares) \| shares				160,000,000	160,000,000
Common stock, votes per share \| vote				1
Sale of stock, number of shares issued (in shares) \| shares			3,156,200
Sale of stock, price per share (USD per share) \| $ / shares			$ 9.87
Proceeds from stock offering, net \| $			$ 30.2
Preferred stock, shares authorized (in shares) \| shares				5,000,000
2019 ATM Offering
Subsidiary, Sale of Stock [Line Items]
Aggregate offering price shares \| $		$ 50.0
Sales commission percentage		3.00%
Public Offering, March 2021
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares issued (in shares) \| shares			5,750,000
Sale of stock, price per share (USD per share) \| $ / shares			$ 11.25
Proceeds from stock offering, net \| $			$ 60.6
2021 ATM Offering
Subsidiary, Sale of Stock [Line Items]
Aggregate offering price shares \| $	$ 75.0
Sales commission percentage	3.00%

Jounce Therapeutics, Inc. 10-K/A