Revenue - Changes in contract assets and contract liabilities (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Contract assets
Net change in contract assets	$ (386)
Contract liabilities
Increases due to cash received, net of amounts recognized as revenue during the period	41,170	$ 182,052
Contract liabilities assumed as part of acquisition	3,818	35,727
Revenue recognized that was included in the contract liability balance as of the beginning of the period	(100,373)	(110,974)
Net change in contract liabilities	(55,385)	106,805
Sales of fuel cell systems
Contract assets
Transferred to receivables from contract assets recognized at the beginning of the period	(12,096)	(14,638)
Contract assets assumed as part of acquisition		9,960
Revenue recognized and not billed as of the end of the period	12,482	25,246
Net change in contract assets	$ 386	$ 20,568