Earnings Per Share - Schedule of Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator (basic and diluted):
Income (loss) from continuing operations attributable to EnPro Industries, Inc.	$ (21.6)	$ (8.4)	$ (14.8)	$ 16.0
Income from discontinued operations, net of taxes	1.9	6.9	207.3	19.5
Net income (loss) attributable to EnPro Industries, Inc.	$ (19.7)	$ (1.5)	$ 192.5	$ 35.5
Denominator:
Weighted-average shares – basic (in shares)	20.5	20.6	20.5	20.7
Share-based awards (in shares)	0.0	0.0	0.0	0.1
Weighted-average shares – diluted (in shares)	20.5	20.6	20.5	20.8
Basic earnings (loss) per share attributable to EnPro Industries, Inc.:
Continuing operations (in dollars per share)	$ (1.05)	$ (0.41)	$ (0.72)	$ 0.77
Discontinued operations (in dollars per share)	0.09	0.33	10.09	0.94
Net income per share (in dollars per share)	(0.96)	(0.08)	9.37	1.71
Diluted earnings (loss) per share attributable to EnPro Industries, Inc.:
Continuing operations (in dollars per share)	(1.05)	(0.41)	(0.72)	0.77
Discontinued operations (in dollars per share)	0.09	0.33	10.09	0.94
Net income (loss) per share (in dollars per share)	$ (0.96)	$ (0.08)	$ 9.37	$ 1.71
Antidilutive securities excluded (in shares)	0.1	0.1	0.1