v3.26.3
Revenue Recognition - Contract Assets and Liabilities (Details) - USD ($)
$ in Thousands
Sep. 30, 2026
Dec. 31, 2025
Contracts with Customers, Asset and Liability [Line Items]    
Advance billings on contracts $ 428,342 $ 305,285
Location, Statement of Financial Position, Balance [Axis]: bwxt:AccountsReceivableRetainage    
Contracts with Customers, Asset and Liability [Line Items]    
Contract with customer, asset 98,219 46,311
Location, Statement of Financial Position, Balance [Axis]: bwxt:CostInExcessOfBillingsCurrent1    
Contracts with Customers, Asset and Liability [Line Items]    
Contract with customer, asset $ 714,269 $ 594,749