GUARANTOR SUBSIDIARIES FINANCIAL INFORMATION - Income Statement (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Total net sales	$ 2,368.4	$ 2,001.7	$ 2,236.3	$ 1,593.6	$ 1,117.8	$ 1,077.8	$ 1,111.7	$ 1,056.2	$ 8,200.0	$ 4,363.5	$ 3,881.7
Cost of sales									(5,922.0)	(3,129.6)	(2,816.4)
Gross profit	674.9	599.4	614.7	389.0	297.0	302.0	324.0	310.9	2,278.0	1,233.9	1,065.3
Total operating expenses									(1,614.9)	(760.5)	(644.2)
Income from operations	226.1	169.1	200.6	67.3	93.4	125.2	123.5	131.3	663.1	473.4	421.1
Interest expense, net									(219.1)	(112.2)	(77.9)
Other income, net									2.8	6.4	8.9
Equity earnings (loss)									0.0	0.0	0.0
Income from operations before income taxes									446.8	367.6	352.1
Income tax expense									(120.3)	(75.9)	(89.8)
Net income									326.5	291.7	262.3
Less: Net loss attributable to noncontrolling interest									0.2	3.2	0.0
Net income attributable to Wabtec shareholders	$ 135.7	$ 91.1	$ 104.1	$ (4.2)	$ 34.4	$ 87.7	$ 84.4	$ 88.4	326.7	294.9	262.3
Comprehensive income (loss) attributable to Wabtec shareholders									200.7	83.3	596.9
Elimination
Condensed Financial Statements, Captions [Line Items]
Total net sales									(1,535.0)	(232.8)	(129.3)
Cost of sales									1,198.7	132.3	98.7
Gross profit									(336.3)	(100.5)	(30.6)
Total operating expenses									0.0	0.0	0.0
Income from operations									(336.3)	(100.5)	(30.6)
Interest expense, net									0.0	0.0	0.0
Other income, net									0.0	0.0	0.0
Equity earnings (loss)									(1,422.9)	(766.3)	(733.7)
Income from operations before income taxes									(1,759.2)	(866.8)	(764.3)
Income tax expense									0.0	0.0	0.0
Net income									(1,759.2)	(866.8)	(764.3)
Less: Net loss attributable to noncontrolling interest									0.0	0.0	0.0
Net income attributable to Wabtec shareholders									(1,759.2)	(866.8)	(764.3)
Comprehensive income (loss) attributable to Wabtec shareholders									(1,759.2)	(866.8)	(764.3)
Parent | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Total net sales									723.4	671.0	577.4
Cost of sales									(562.1)	(495.1)	(440.9)
Gross profit									161.3	175.9	136.5
Total operating expenses									(321.6)	(173.0)	(114.2)
Income from operations									(160.3)	2.9	22.3
Interest expense, net									(214.8)	(110.8)	(76.8)
Other income, net									(131.5)	13.5	10.0
Equity earnings (loss)									809.5	396.9	416.1
Income from operations before income taxes									302.9	302.5	371.6
Income tax expense									23.8	(7.6)	(109.3)
Net income									326.7	294.9	262.3
Less: Net loss attributable to noncontrolling interest									0.0	0.0	0.0
Net income attributable to Wabtec shareholders									326.7	294.9	262.3
Comprehensive income (loss) attributable to Wabtec shareholders									326.7	295.8	263.9
Guarantors | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Total net sales									3,245.3	483.1	398.2
Cost of sales									(2,429.2)	(304.3)	(255.8)
Gross profit									816.1	178.8	142.4
Total operating expenses									(311.5)	(57.3)	(50.9)
Income from operations									504.6	121.5	91.5
Interest expense, net									12.5	12.8	10.9
Other income, net									(11.1)	0.0	0.3
Equity earnings (loss)									613.4	369.4	317.6
Income from operations before income taxes									1,119.4	503.7	420.3
Income tax expense									(97.0)	(3.3)	18.8
Net income									1,022.4	500.4	439.1
Less: Net loss attributable to noncontrolling interest									0.0	0.0	0.0
Net income attributable to Wabtec shareholders									1,022.4	500.4	439.1
Comprehensive income (loss) attributable to Wabtec shareholders									1,022.4	500.4	439.1
Non-Guarantors | Reportable Legal Entities
Condensed Financial Statements, Captions [Line Items]
Total net sales									5,766.3	3,442.2	3,035.4
Cost of sales									(4,129.4)	(2,462.5)	(2,218.4)
Gross profit									1,636.9	979.7	817.0
Total operating expenses									(981.8)	(530.2)	(479.1)
Income from operations									655.1	449.5	337.9
Interest expense, net									(16.8)	(14.2)	(12.0)
Other income, net									145.4	(7.1)	(1.4)
Equity earnings (loss)									0.0	0.0	0.0
Income from operations before income taxes									783.7	428.2	324.5
Income tax expense									(47.1)	(65.0)	0.7
Net income									736.6	363.2	325.2
Less: Net loss attributable to noncontrolling interest									0.2	3.2	0.0
Net income attributable to Wabtec shareholders									736.8	366.4	325.2
Comprehensive income (loss) attributable to Wabtec shareholders									$ 610.8	$ 153.9	$ 658.2