Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Jul. 30, 2020
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2020
Document Transition Report	false
Entity File Number	001-34658
Entity Registrant Name	BWX TECHNOLOGIES, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	80-0558025
Entity Address, Address Line One	800 Main Street, 4th Floor
Entity Address, City or Town	Lynchburg,
Entity Address, State or Province	VA
Entity Address, Postal Zip Code	24504
City Area Code	980
Local Phone Number	365-4300
Title of 12(b) Security	Common Stock, $0.01 par value
Trading Symbol	BWXT
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding (in shares)		95,289,392
Amendment Flag	false
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Central Index Key	0001486957
Current Fiscal Year End Date	--12-31