Revenue - Estimated future revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($)
Revenue
Total estimated future revenue	$ 494,443
Sales of fuel cell systems
Revenue
Total estimated future revenue	66,033
Sale of hydrogen installations and other infrastructure
Revenue
Total estimated future revenue	69,678
Services performed on fuel cell systems and related infrastructure
Revenue
Total estimated future revenue	105,852
Power Purchase Agreements
Revenue
Total estimated future revenue	185,431
Fuel delivered to customers
Revenue
Total estimated future revenue	64,555
Other
Revenue
Total estimated future revenue	$ 2,894
Maximum | Sales of fuel cell systems
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	1 year
Maximum | Services performed on fuel cell systems and related infrastructure
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	7 years
Maximum | Power Purchase Agreements
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	7 years
Minimum | Services performed on fuel cell systems and related infrastructure
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	5 years
Minimum | Power Purchase Agreements
Revenue
Duration of estimated revenue expected to be recognized in future (in years)	5 years