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Basis of Presentation and Significant Accounting Policies - Additional Information (Detail) $ in Thousands |  | 12 Months Ended
--- | --- | ---
May 29, 2020 USD ($) | Dec. 31, 2020 USD ($) component segment facilities | Dec. 31, 2019 USD ($) | Dec. 31, 2018 USD ($)
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Number of reportable segments | segment |  | 3 |  |
Number of large, heavy components supplied to worldwide (more than) | component |  | 1,300 |  |
Research and development activities |  | $ 40,800 | $ 66,900 | $ 63,400
Research and development activities, paid by customers |  | 26,600 | 49,200 | 48,200
Interest expense |  | 40,800 | 41,400 | 31,500
Interest costs capitalized |  | 9,800 | 6,100 | 3,700
Restricted cash and cash equivalents reclassified into other assets |  | 5,700 |  |
Restricted cash and cash equivalents |  | 3,070 | 3,056 |
Total inventories |  | 15,000 | 17,100 |
Depreciation |  | 50,300 | 51,000 | 48,600
Lease expense |  | 7,700 | 8,100 | 6,200
Cash payments for leases |  | $ 6,200 |  |
Weighted average remaining lease term |  | 5 years 7 months 6 days |  |
Weighted average discount rate |  | 4.64% |  |
Operating lease, right-of-use asset |  | $ 41,300 |  |
Number of facilities with U.S. Government decommissioning costs obligation | facilities |  | 2 |  |
Reserves for self-insurance |  | $ 5,000 | 5,200 |
Net foreign currency transaction gains (losses) |  | (600) | 1,000 | 2,000
Net gains deferred on derivative financial instruments in accumulated other comprehensive income (loss) |  | (500) |  |
Gains recognized in other-net associated with derivative financial instruments |  | 8,700 | $ (1,000) | $ (4,700)
Notional amount of foreign currency forward contracts |  | $ 245,300 |  |
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List] |  | us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent | us-gaap:AccountsPayableAndAccruedLiabilitiesCurrent |
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List] |  | us-gaap:OtherLiabilitiesNoncurrent | us-gaap:OtherLiabilitiesNoncurrent |
Favorable operating lease |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Amortization |  | $ 1,500 |  |
Nuclear Services Business |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Net assets exchanged in noncash transaction | $ 18,000 |  |  |
Accounts Receivable |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Canada Emergency Wage Subsidy (CEWS) grant |  | $ 20,400 |  |
Minimum |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Operating lease contract term |  | 1 year |  |
Operating lease renewal contract term |  | 1 year |  |
Minimum | Machinery and equipment |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Useful life |  | 3 years |  |
Minimum | Property, Plant and Equipment |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Useful life |  | 8 years |  |
Maximum |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Operating lease contract term |  | 20 years |  |
Operating lease renewal contract term |  | 10 years |  |
Maximum | Machinery and equipment |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Useful life |  | 14 years |  |
Maximum | Property, Plant and Equipment |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Useful life |  | 40 years |  |
Cash Held For Decommissioning Of Facilities |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Restricted cash and cash equivalents |  | $ 2,600 |  |
Cash Held To Meet Reinsurance Reserve Requirements |  |  |  |
Basis Of Presentation And Significant Accounting Policies [Line Items] |  |  |  |
Restricted cash and cash equivalents |  | $ 3,100 |  |

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