Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2021	Sep. 30, 2020	Jun. 30, 2020	May 31, 2020	May 29, 2020	May 18, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Mar. 31, 2018
Summary of Significant Accounting Policies
Loss accrual	$ 24,013	$ 3,702	$ 5,345
Operating lease maximum allowed extension percentage	75.00%
Minimum number of days after an invoice is issued when accounts receivable is considered due	30 days
Maximum number of days after an invoice is issued when accounts receivable is considered due	60 days
Allowance for doubtful accounts receivable	$ 172	249
Accumulated deficit	(1,946,488)	(1,350,307)			$ (1,462,377)	$ (1,397,160)				$ (1,387,752)	$ (1,332,259)	$ (1,314,425)	$ (1,297,072)
Additional paid-in capital	3,446,650	1,506,953			$ 2,083,169	$ 1,658,438				$ 1,519,094	$ 1,340,781	$ 1,325,381	$ 1,316,815
Interest rate (as a percent)							3.50%
Stock-Based Compensation
Tax benefit (expense) for stock-based compensation	$ 0	$ 0	$ 0
Fuel
Property, Plant and Equipment
Estimated useful life	10 years
Hydrogen infrastructure
Property, Plant and Equipment
Estimated useful life	20 years
Minimum
Summary of Significant Accounting Policies
Payment terms for fuel cells and its services	30 days
Extension period	5 years
Uptime of the fleet (as a percent)	97.00%
Intangible Assets
Intangible asset useful lives	5 years
Maximum
Summary of Significant Accounting Policies
Payment terms for fuel cells and its services	90 days
Extension period	10 years
Uptime of the fleet (as a percent)	98.00%
Intangible Assets
Intangible asset useful lives	10 years
Leasehold Improvements | Minimum
Property, Plant and Equipment
Estimated useful life	5 years
Leasehold Improvements | Maximum
Property, Plant and Equipment
Estimated useful life	10 years
Software, machinery and equipment | Minimum
Property, Plant and Equipment
Estimated useful life	1 year
Software, machinery and equipment | Maximum
Property, Plant and Equipment
Estimated useful life	15 years
3.75% Convertible Senior Notes
Summary of Significant Accounting Policies
Interest rate (as a percent)	3.75%						3.75%	3.75%	3.75%
5.5% Convertible Senior Notes
Summary of Significant Accounting Policies
Interest rate (as a percent)	5.50%						5.50%		5.50%					5.50%
Cumulative Adjustment
Summary of Significant Accounting Policies
Convertible Debt				$ 120,700
Accumulated deficit				9,500
Additional paid-in capital				$ 130,200