Revenue - Changes in contract assets and contract liabilities (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($)
Contract assets
Net change in contract assets	$ (10,608)
Sales of fuel cell systems
Contract assets
Transferred to receivables from contract assets recognized at the beginning of the period	(14,638)
Contract assets assumed as part of acquisitions	9,960
Revenue recognized and not billed as of the end of the period	25,246
Net change in contract assets	20,568
Contract liabilities
Increases due to cash received, net of amounts recognized as revenue during the period	182,052
Contract liabilities assumed as part of acquisitions	35,727
Revenue recognized that was included in the contract liability balance as of the beginning of the period	(110,974)
Net change in contract liabilities	$ 106,805