Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net Income	$ 66,413	$ 55,786
Other Comprehensive Income (Loss):
Currency translation adjustments	(3,124)	791
Derivative financial instruments:
Unrealized gains arising during the period, net of tax provision of $(59) and $(97), respectively	173	279
Reclassification adjustment for gains included in net income, net of tax provision of $30 and $13, respectively	(79)	(37)
Amortization of benefit plan costs, net of tax benefit of $(183) and $(156), respectively	322	290
Investments:
Unrealized losses arising during the period, net of tax benefit (provision) of $0 and $(70), respectively	(66)	(94)
Reclassification adjustment for gains included in net income, net of tax provision of $0 and $8, respectively	0	(14)
Other Comprehensive Income (Loss)	(2,774)	1,215
Total Comprehensive Income	63,639	57,001
Comprehensive (Income) Loss Attributable to Noncontrolling Interest	28	(67)
Comprehensive Income Attributable to BWX Technologies, Inc.	$ 63,667	$ 56,934