Revenue - Changes in contract assets and contract liabilities (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Dec. 31, 2023
Contract assets
Net change in contract assets	$ 2,897	$ 23,807
Contract liabilities
Increases due to customer billings, net of amounts recognized as revenue during the period	21,195		$ 151,965
Change in contract liabilities related to warrants	219		440
Revenue recognized that was included in the contract liability balance as of the beginning of the period	(63,870)		(94,001)
Net change in deferred revenue and contract liabilities	(42,456)		58,404
Sales of fuel cell systems
Contract assets
Transferred to receivables from contract assets recognized at the beginning of the period	(12,959)		(94,860)
Change in contract assets related to warrants	3,766		14,260
Impairment			(2,375)
Revenue recognized and not billed as of the end of the period	15,635		134,677
Net change in contract assets	$ 6,442		$ 51,702