Intangible Assets - Gross Carrying Amount (Details) - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	May 31, 2019
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Gross Carrying Amount	$ 42,002		$ 8,564
Accumulated Amortization	(3,428)		(3,025)
Total	38,574		5,539
Payments to Acquire Intangible Assets		$ 1,860
Payables for acquiring Intellectual Property	23,320		$ 14,213
EnergyOr
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Acquired		$ 1,500
Milestone payments				$ 3,000
American Fuel Cell LLC
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Milestone payments	2,900
Payments to Acquire Intangible Assets	400
Payables for acquiring Intellectual Property	1,700
In process R&D
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Gross Carrying Amount	29,000
Total	$ 29,000
Acquired technology
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	10 years		9 years
Gross Carrying Amount	$ 12,112		$ 8,244
Accumulated Amortization	(3,205)		(2,815)
Total	$ 8,907		$ 5,429
Customer relationships, Backlog & Trademark
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period	8 years
Gross Carrying Amount	$ 890
Accumulated Amortization	(223)
Total	$ 667
Customer Relationships And Trademark [Member]
Gross carrying amount and accumulated amortization of acquired identifiable intangible assets
Weighted Average Amortization Period			9 years
Gross Carrying Amount			$ 320
Accumulated Amortization			(210)
Total			$ 110