Fair value measurements - Summary of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024	Mar. 31, 2024	Dec. 31, 2023
Assets:
Marketable securities:	$ 81,006	$ 112,377
Restricted cash and cash equivalents	102,019	72,865	$ 57,025	$ 76,683
U.S. government agency securities and treasuries
Assets:
Marketable securities:	58,069	67,764
Corporate bonds
Assets:
Marketable securities:	2,004	2,010
Commercial paper
Assets:
Marketable securities:	20,933	42,603
Fair Value, Measurements, Recurring
Assets:
Cash and cash equivalents	92,356	71,244
Restricted cash and cash equivalents	9,663	1,621
Restricted investments	26,329	33,864
Total assets	209,354	219,106
Liabilities:
Contingent consideration		0
Total liabilities		0
Fair Value, Measurements, Recurring \| U.S. government agency securities and treasuries
Assets:
Marketable securities:	58,069	67,764
Fair Value, Measurements, Recurring \| Corporate bonds
Assets:
Marketable securities:	2,004	2,010
Fair Value, Measurements, Recurring \| Commercial paper
Assets:
Marketable securities:	20,933	42,603
Fair Value, Measurements, Recurring \| Quoted prices in active markets (Level 1)
Assets:
Cash and cash equivalents	92,356	71,244
Restricted cash and cash equivalents	9,663	1,621
Restricted investments	0	0
Total assets	102,019	72,865
Liabilities:
Contingent consideration		0
Total liabilities		0
Fair Value, Measurements, Recurring \| Quoted prices in active markets (Level 1) \| U.S. government agency securities and treasuries
Assets:
Marketable securities:	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets (Level 1) \| Corporate bonds
Assets:
Marketable securities:	0	0
Fair Value, Measurements, Recurring \| Quoted prices in active markets (Level 1) \| Commercial paper
Assets:
Marketable securities:	0	0
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Restricted cash and cash equivalents	0	0
Restricted investments	26,329	33,864
Total assets	107,335	146,241
Liabilities:
Contingent consideration		0
Total liabilities		0
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| U.S. government agency securities and treasuries
Assets:
Marketable securities:	58,069	67,764
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Corporate bonds
Assets:
Marketable securities:	2,004	2,010
Fair Value, Measurements, Recurring \| Significant other observable inputs (Level 2) \| Commercial paper
Assets:
Marketable securities:	20,933	42,603
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Restricted cash and cash equivalents	0
Restricted investments	0	0
Total assets	0	0
Liabilities:
Contingent consideration		0
Total liabilities		0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| U.S. government agency securities and treasuries
Assets:
Marketable securities:	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Corporate bonds
Assets:
Marketable securities:	0	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs (Level 3) \| Commercial paper
Assets:
Marketable securities:	$ 0	$ 0

2seventy bio, Inc. 10-Q