Fair value of financial assets and liabilities (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2025	Mar. 31, 2025
Fair value of financial assets and liabilities
Short-term investments	$ 396,725	$ 462,564
Money market funds
Fair value of financial assets and liabilities
Cash equivalents	90,758	89,879
US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	58,497	84,804
US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	247,470	287,881
Level 1
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 1 | Money market funds
Fair value of financial assets and liabilities
Cash equivalents	0	0
Level 1 | US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 1 | US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 2
Fair value of financial assets and liabilities
Short-term investments	396,725	462,564
Level 2 | Money market funds
Fair value of financial assets and liabilities
Cash equivalents	90,758	89,879
Level 2 | US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	58,497	84,804
Level 2 | US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	247,470	287,881
Level 3
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 3 | Money market funds
Fair value of financial assets and liabilities
Cash equivalents	0	0
Level 3 | US Government Agency bonds
Fair value of financial assets and liabilities
Short-term investments	0	0
Level 3 | US Treasury bonds
Fair value of financial assets and liabilities
Short-term investments	$ 0	$ 0