Commitments and contingencies - Other information (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Mar. 31, 2024
Leases
Right-to-use operating lease asset	$ 4,475		$ 4,635
Right-to-use finance lease asset	36,629		37,237
Total lease assets	41,104		41,872
Operating lease liabilities, current	1,164		1,161
Finance lease liabilities, current	2,738		2,718
Operating lease liabilities, non-current	3,600		3,771
Financing lease liabilities, non-current	23,256		23,410
Total lease liabilities	30,758		$ 31,060
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	152	$ 263
Operating cash flows from finance leases	534	544
Financing cash flows from finance leases	134	104
Right-to-use asset obtained in exchange for new operating lease liabilities	$ 0	$ 0
Weighted-average remaining lease term - operating leases	5 years 7 months 6 days	6 years 3 months 18 days
Weighted-average remaining lease term - financing leases	15 years 3 months 18 days	16 years 1 month 6 days
Weighted-average discount rate - operating leases	10.30%	10.30%
Weighted-average discount rate - financing leases	8.30%	8.30%