STOCK-BASED COMPENSATION - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024	Dec. 31, 2027	Dec. 31, 2026	Dec. 31, 2025
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 24	$ 17	$ 44	$ 34
Unamortized compensation expense expected to be vested	$ 119		$ 119
Granted (in shares)			0
Exercisable at period end (in shares)	95,551		95,551
Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			3 years
Plan term			10 years
Performance Shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			3 years
Share-based compensation, relative total stockholder return modifier, payment percentage, increase			10.00%
Share-based compensation, relative total stockholder return modifier, payment percentage, decrease			20.00%
Percentage of incentive stock awards expected to be vested and awarded of stocks granted			100.00%
Performance Shares \| Scenario Forecast
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of incentive stock awards expected to be vested and awarded of stocks granted					116.00%	200.00%	186.00%
Performance Shares \| Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of incentive stock awards expected to be vested and awarded of stocks granted			0.00%
Performance Shares \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of incentive stock awards expected to be vested and awarded of stocks granted			200.00%
2011 and 2000 Plans \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			3 years
2011 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares available for grant (in shares)	3,900,000		3,900,000
Directors Plan \| Restricted Stock
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Award vesting period			1 year

WESTINGHOUSE AIR BRAKE TECHNOLOGIES CORP 10-Q