Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue
Net revenue	$ 68,070	$ 57,535	$ 108,883	$ 79,114
Sales of fuel cell systems
Revenue
Net revenue	41,264	38,696	55,915	41,240
Sale of hydrogen installations and other infrastructure
Revenue
Net revenue	6,482		12,218
Services performed on fuel cell systems and related infrastructure
Revenue
Net revenue	6,236	5,341	12,757	11,684
Power Purchase Agreements
Revenue
Net revenue	6,654	6,409	13,150	12,519
Fuel delivered to customers
Revenue
Net revenue	7,372	$ 7,089	14,705	$ 13,671
Other
Revenue
Net revenue	$ 62		$ 138