Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 75,620	$ 49,110
Other Comprehensive Income (Loss):
Currency translation adjustments	(11,940)	943
Derivative financial instruments:
Unrealized gains (losses) arising during the period, net of tax (provision) benefit of $(109) and $164, respectively	313	(441)
Reclassification adjustment for losses (gains) included in net income, net of tax (benefit) provision of $(138) and $49, respectively	420	(141)
Amortization of benefit plan costs, net of tax benefit of $(167) and $(136), respectively	610	511
Investments:
Unrealized (losses) gains arising during the period, net of tax provision of $(2) and $(7), respectively	(600)	24
Other Comprehensive Income (Loss)	(11,197)	896
Total Comprehensive Income	64,423	50,006
Comprehensive Income Attributable to Noncontrolling Interest	(121)	(132)
Comprehensive Income Attributable to BWX Technologies, Inc.	$ 64,302	$ 49,874