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v3.20.4

Segment Reporting - Schedule of Revenue Information from Products and Service Lines (Details) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended
--- | --- | ---
Dec. 31, 2020 | Sep. 30, 2020 | Jun. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues | $ 556,910 | $ 519,878 | $ 504,520 | $ 542,208 | $ 501,235 | $ 506,000 | $ 471,231 | $ 416,454 | $ 2,123,516 | $ 1,894,920 | $ 1,799,889
Nuclear Power Group |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 371,269 | 352,640 | 365,911
Nuclear Services Group |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 136,493 | 131,339 | 122,438
Nuclear Operations Group |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 1,646,257 | 1,428,587 | 1,319,170
Reportable Segments |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 2,154,019 | 1,912,566 | 1,807,519
Reportable Segments | Nuclear Power Group |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 371,269 | 352,640 | 365,911
Reportable Segments | Nuclear Power Group | Nuclear Services and Engineering |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 120,684 | 109,168 | 164,283
Reportable Segments | Nuclear Power Group | Nuclear Services and Engineering |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 250,585 | 243,472 | 201,628
Reportable Segments | Nuclear Services Group |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 136,493 | 131,339 | 122,438
Reportable Segments | Nuclear Services Group | Nuclear Environmental Services |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 94,320 | 102,726 | 96,566
Reportable Segments | Nuclear Services Group | Nuclear Services and Advanced Reactor Design and Engineering |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 42,173 | 28,613 | 25,872
Reportable Segments | Nuclear Operations Group |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 1,646,257 | 1,428,587 | 1,319,170
Reportable Segments | Nuclear Operations Group | Government Programs |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 1,540,256 | 1,368,555 | 1,311,886
Reportable Segments | Nuclear Operations Group | Commercial Operations |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | 106,001 | 60,032 | 7,284
Other |  |  |  |  |  |  |  |  |  |  |
Revenue from External Customer [Line Items] |  |  |  |  |  |  |  |  |  |  |
Revenues |  |  |  |  |  |  |  |  | $ (30,503) | $ (17,646) | $ (7,630)

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