Revenue - Estimated future revenue (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Revenue
Total estimated future revenue	$ 389,936
Sales of fuel cell systems
Revenue
Total estimated future revenue	76,433
Sale of hydrogen installations and other infrastructure
Revenue
Total estimated future revenue	69,440
Services performed on fuel cell systems and related infrastructure
Revenue
Total estimated future revenue	97,530
Power Purchase Agreements
Revenue
Total estimated future revenue	142,002
Other
Revenue
Total estimated future revenue	$ 4,531
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