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The Company - Going Concern (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2021 | Dec. 31, 2021 | Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |
Proceeds from sale of convertible preferred units | $ 40,500 | $ 192,500 | $ 18,500
NuScale SMR FOAK Nuclear Demonstration Readiness Project Completion |  |  |
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items] |  |  |
Cumulative cash received |  | 57,817 | $ 100,500
Proceeds from sale of convertible preferred units |  | $ 192,500 |

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- Definition The cash inflow from issuance of preferred stocks identified as being convertible into another form of financial instrument, typically the entity's common stock. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3255-108585 + Details
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