Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue
Net revenue	$ 309,099	$ 107,048	$ 67,995	$ 40,819	$ 91,607	$ 59,392	$ 57,466	$ 21,510		$ 78,976		$ 138,368
Net revenue		107,048	67,995	40,819	91,607				$ 108,814		$ 215,862		$ (93,237)	$ 229,975	$ 174,215
Sales of fuel cell systems
Revenue
Net revenue													(55,091)	130,757	75,029
Sale of hydrogen installations and other infrastructure
Revenue
Net revenue													(39,204)	19,163	32,146
Services performed on fuel cell systems and related infrastructure
Revenue
Net revenue	(29,387)	6,829	6,236	6,521	7,328	6,205	5,341	6,343	12,757	11,684	19,586	17,889	(9,801)	25,217	22,002
Power Purchase Agreements
Revenue
Net revenue	6,991	6,629	6,579	6,421	6,664	6,520	6,334	6,035	13,000	12,369	19,629	18,889	26,620	25,553	22,569
Fuel delivered to customers
Revenue
Net revenue	(40,608)	9,831	7,372	7,333	7,779	7,649	$ 7,089	$ 6,582	14,705	$ 13,671	24,536	21,320	(16,072)	29,099	$ 22,469
Other
Revenue
Net revenue	$ 76	$ 97	$ 62	$ 76	$ 51	$ 135			$ 138		$ 235	$ 135	$ 311	$ 186