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Mezzanine and Members' Equity - Preferred Units Purchase Agreement (Details) - USD ($) $ / shares in Units, $ in Thousands | Mar. 31, 2022 | Dec. 31, 2021 | Jul. 31, 2021 | Jun. 30, 2021 | May 31, 2021 | Mar. 31, 2021 | Jan. 31, 2021 | Dec. 31, 2020 | Nov. 30, 2020 | Oct. 31, 2020 | Aug. 31, 2020
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Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Investment | $ 819,694 | $ 819,694 |  |  |  |  |  | $ 629,089 |  |  |
Fluor Enterprises [Member] |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  |  |  |  |  |  | $ 1.92 |  |  | $ 1.92
Investment |  | $ 0 |  |  |  |  |  | $ 10,000 |  |  | $ 10,000
JGC Holdings Corporation |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  |  |  |  | $ 1.92 |  |  |  |  |
Investment |  |  |  |  |  | $ 40,000 |  |  |  |  |
Sargent & Lundy, L.L.C [Member] |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  | $ 2.19 |  |  |  |  |  | $ 1.92 |  |
Investment |  |  | $ 8,000 |  |  |  |  |  | $ 8,000 |  |
Sarens Nuclear & Industrial Services, LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  | $ 2.19 |  |  |  | $ 1.92 |  |  | $ 1.92 |
Investment |  |  | $ 4,000 |  |  |  | $ 500 |  |  | $ 500 |
Japan NuScale Innovation, LLC [Member] |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  |  |  | $ 2.19 | $ 1.92 |  |  |  |  |
Investment |  |  |  |  | $ 20,000 | $ 40,000 |  |  |  |  |
GS Energy Corporation |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  |  | $ 2.19 |  |  |  |  |  |  |
Investment |  |  |  | $ 40,000 |  |  |  |  |  |  |
Doosan Heavy Industries & Construction Co., Ltd |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  | $ 2.19 |  |  |  |  |  |  |  |
Investment |  |  | $ 25,000 |  |  |  |  |  |  |  |
Next Tech 3 New Technology Investment |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  | $ 2.19 |  |  |  |  |  |  |  |
Investment |  |  | $ 35,000 |  |  |  |  |  |  |  |
Samsung C&T Corporation |  |  |  |  |  |  |  |  |  |  |
Preferred Units [Line Items] |  |  |  |  |  |  |  |  |  |  |
Share price per share |  |  | $ 2.19 |  |  |  |  |  |  |  |
Investment |  |  | $ 20,000 |  |  |  |  |  |  |  |

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- Definition The amount of the preferred partners' ownership interests. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 5 -Subparagraph (SAB Topic 4.F) -URI http://asc.fasb.org/extlink&oid=120397183&loc=d3e187171-122770 + Details
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