Unaudited Quarterly Financial data and Restatement of Previously Issued Unaudited Interim Condensed Consolidated Financial Statements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended		12 Months Ended
	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
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Long-term Line of Credit												$ 175,400
Property, Plant, and Equipment, Lessor Asset under Operating Lease, after Accumulated Depreciation	$ 71,891	$ 68,428	$ 68,402	$ 67,769	$ 67,248	$ 68,982	$ 70,928	$ 68,428	$ 68,982	$ 71,891	$ 67,248	75,807	$ 67,769
Other Liabilities, Noncurrent	45,170	14,476	2,386	2,818	2,834	3,333	3,746	14,476	3,333	45,170	2,834	40,447	2,818
Operating Lease, Liability												113,938
Accounts receivable	113,505	45,782	24,734	25,768	24,737	26,844	32,307	45,782	26,844	113,505	24,737	43,041	25,768
Inventory, Net	134,203	114,571	92,972	72,391	80,601	73,190	65,474	114,571	73,190	134,203	80,601	139,386	72,391
Prepaid Expense and Other Assets, Current	26,731	31,436	28,500	21,192	12,804	14,001	10,296	31,436	14,001	26,731	12,804	44,324	21,192
Goodwill	71,822	70,262	8,673	8,842	8,606	8,961	8,886	70,262	8,961	71,822	8,606	72,387	8,842
Operating Lease, Right-of-Use Asset	90,184	71,789	64,812	63,266	47,016	39,679	33,599	71,789	39,679	90,184	47,016	117,016	63,266
Intangible Assets, Net (Excluding Goodwill)	39,569	38,974	5,696	5,539	5,113	5,398	3,677	38,974	5,398	39,569	5,113	39,251	5,539
Accrued Liabilities, Current	37,948	23,917	14,870	14,409	9,457	4,522	6,509	23,917	4,522	37,948	9,457	46,083	14,409
Other Liabilities, Current	21,083	19,418	8,446	6,704	8,373	3,705	3,745	19,418	3,705	21,083	8,373	29,487	6,704
Deferred Revenue, Noncurrent	29,511	24,848	22,684	23,170	22,213	24,126	25,366	24,848	24,126	29,511	22,213	32,944	23,170
Other assets	9,661	11,817	12,059	8,573	9,152	8,842	11,069	11,817	8,842	9,661	9,152	5,513	8,573
Accounts payable	58,793	39,812	35,503	40,376	36,851	36,946	31,688	39,812	36,946	58,793	36,851	50,198	40,376
Convertible senior notes, net	105,088	142,889	113,063	110,431	107,945	66,844	65,025	142,889	66,844	105,088	107,945	85,640	110,431
Additional Paid in Capital	2,083,169	1,658,438	1,519,094	1,506,953	1,340,781	1,325,381	1,316,815	1,658,438	1,325,381	2,083,169	1,340,781	3,446,650	1,506,953
Accumulated Other Comprehensive Income (Loss), Net of Tax	1,846	1,159	1,052	1,288	929	1,460	1,374	1,159	1,460	1,846	929	2,451	1,288
Research and Development Expense	7,386	4,873	4,774	4,882	3,563	3,608	3,006	9,647	6,614	17,033	10,177	27,848	15,059	$ 12,750
Cost of Goods and Services Sold	135,632	68,010	50,522	83,861	54,892	51,324	29,250	118,532	80,574	254,164	135,466	376,179	219,327	200,219
Nonoperating Income (Expense)	(17,551)	(13,462)	(11,846)	(10,999)	(8,273)	(7,965)	(8,454)	(25,308)	(16,419)	(42,859)	(24,692)	(60,484)	(35,691)	(22,750)
Selling, General and Administrative Expense	17,210	21,644	11,109	9,973	10,395	13,613	9,221	32,753	22,834	49,963	33,229	79,348	43,202	37,685
Income tax benefit	6,644	17,371						17,371		24,015		30,845		9,295
Net revenue	107,048	67,995	40,819	91,607				108,814		215,862		(93,237)	229,975	174,215
Net Cash Provided by (Used in) Operating Activities			(60,402)				(35,699)	(111,891)	(48,328)	(156,506)	(54,141)	(155,476)	(53,324)	(58,350)
Repayments of Debt			5,343				53,580	11,129	55,712	19,038	56,603	27,212	59,196	30,531
Accumulated deficit	(1,462,377)	(1,397,160)	(1,387,752)	(1,350,307)	(1,332,259)	(1,314,425)	(1,297,072)	(1,397,160)	(1,314,425)	(1,462,377)	(1,332,259)	(1,946,488)	(1,350,307)
Bonus Accrual
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other Labor-related Expenses	5,300									5,300
ROU assets and lease liabilities
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Other Labor-related Expenses										2,400
As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Property, Plant, and Equipment, Lessor Asset under Operating Lease, after Accumulated Depreciation	309,475	274,721	252,802	244,740	202,034	170,455	141,889	274,721	170,455	309,475	202,034		244,740
Other Liabilities, Noncurrent	27,068	11,756	13	13	13	13	17	11,756	13	27,068	13		13
Accounts receivable	113,133	45,522	24,437	25,448	24,392	26,592	32,062	45,522	26,592	113,133	24,392		25,448
Inventory, Net	134,306	114,571	92,972	72,391	80,601	73,190	65,474	114,571	73,190	134,306	80,601		72,391
Prepaid Expense and Other Assets, Current	26,731	31,436	28,500	21,192	12,804	14,001	10,296	31,436	14,001	26,731	12,804		21,192
Goodwill	71,962	70,402	8,673	8,842	8,606	8,961	8,886	70,402	8,961	71,962	8,606		8,842
Intangible Assets, Net (Excluding Goodwill)	39,169	38,574	5,296	5,539	5,113	5,398	3,677	38,574	5,398	39,169	5,113		5,539
Accrued Liabilities, Current	32,031	23,320	14,273	14,213	9,457	4,522	6,509	23,320	4,522	32,031	9,457		14,213
Other Liabilities, Current	17,280	21,692	10,423	8,543	10,238	3,017	2,271	21,692	3,017	17,280	10,238		8,543
Deferred Revenue, Noncurrent	29,648	25,038	22,912	23,369	22,444	24,519	25,835	25,038	24,519	29,648	22,444		23,369
Other assets	9,661	11,817	12,059	8,573	9,152	8,842	11,069	11,817	8,842	9,661	9,152		8,573
Accounts payable	58,793	39,812	35,503	40,376	36,851	36,946	31,688	39,812	36,946	58,793	36,851		40,376
Convertible senior notes, net	105,088	142,704	112,878	110,246	107,760	66,844	65,025	142,704	66,844	105,088	107,760		110,246
Additional Paid in Capital	2,083,199	1,658,532	1,519,257	1,507,116	1,340,859	1,325,459	1,316,893	1,658,532	1,325,459	2,083,199	1,340,859		1,507,116
Accumulated Other Comprehensive Income (Loss), Net of Tax	1,958	1,271	1,164	1,400	929	1,460	1,374	1,271	1,460	1,958	929		1,400
Research and Development Expense	11,964	9,757	10,412	9,341	8,028	8,933	7,373	20,169	16,306	32,133	24,334		33,675	33,907
Cost of Goods and Services Sold	108,279	62,994	45,284	78,882	51,114	46,914	25,363	108,278	72,277	216,557	123,391		202,273	172,010
Nonoperating Income (Expense)	(17,241)	(13,198)	(11,583)	(10,806)	(7,972)	(7,861)	(8,345)	(24,781)	(16,206)	(42,022)	(24,178)		(35,502)	(22,135)
Selling, General and Administrative Expense	14,277	21,658	11,013	10,982	10,400	13,627	9,324	32,671	22,951	46,948	33,351		44,333	38,198
Income tax benefit	6,523	17,659						17,659		24,182				9,217
Net revenue	106,989	68,070	40,813	91,664				108,883		215,872			230,239	174,632
Net Cash Provided by (Used in) Operating Activities			(60,015)				(36,263)	(111,247)	(48,488)	(156,910)	(51,801)		(51,522)	(57,617)
Repayments of Debt			5,730				53,534	11,783	56,070	18,634	59,461		61,713	31,264
Accumulated deficit	(1,431,340)	(1,391,961)	(1,383,299)	(1,345,807)	(1,327,518)	(1,309,363)	(1,291,255)	(1,391,961)	(1,309,363)	(1,431,340)	(1,327,518)		(1,345,807)
Provision (benefit) for loss contracts related to service
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	25,147	706	95	13	206	363	162	801	201	25,948	407	35,473	394	5,345
Provision (benefit) for loss contracts related to service | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	4,306									4,306
Sales of fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	69,428	33,888	13,974	47,091	25,183	23,329	2,312	47,862	25,641	117,290	50,824	171,404	97,915	85,205
Sales of fuel cell systems and related infrastructure | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold													7,000
Sales of fuel cell systems and related infrastructure | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	68,509	33,676	13,744	46,419	24,990	23,129	2,321	47,420	25,450	115,929	50,440		96,859	84,439
Fuel delivered to customers
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	17,002	11,076	11,254	12,800	11,149	11,146	10,152	22,330	21,298	39,332	32,447	61,815	45,247	36,037
Fuel delivered to customers | Revision of Research and Development Expense
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold													8,900
Fuel delivered to customers | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	14,172	9,060	9,035	10,422	9,160	8,854	7,921	18,095	16,775	32,267	25,935		36,357	27,712
Services performed on fuel cell systems and related infrastructure
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	9,180	7,773	10,347	11,606	7,802	8,383	6,791	18,120	15,174	27,300	22,976	42,524	34,582	32,271
Services performed on fuel cell systems and related infrastructure | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	7,074	6,491	8,181	9,999	6,461	6,218	6,123	14,672	12,341	21,746	18,802		28,801	23,698
Power Purchase Agreements
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	14,744	14,504	14,771	12,301	10,814	8,829	9,833	29,275	18,662	44,019	29,476	$ 64,640	41,777	41,361
Power Purchase Agreements | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Cost of Goods and Services Sold	$ 14,087	$ 13,704	$ 14,243	$ 11,992	10,353	8,713	8,998	$ 27,947	17,711	$ 42,034	28,064		$ 40,056	$ 36,161
ASU 2019-08 | As previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Additional Paid in Capital					6,500	3,500	3,000		3,500		6,500
Accumulated deficit					$ 6,500	$ 3,500	$ 3,000		$ 3,500		$ 6,500