REPORTING SEGMENTS AND RELATED INFORMATION - Earnings before interest and income taxes (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Segment Reporting Information
Segment Adjusted EBIT	$ 479	$ 29	$ 992	$ 300
Corporate, including stock-based compensation	78	38	147	75
Restructuring expense	62	37	92	52
Merger, acquisition and divestiture expense	15	21	28	42
Loss on sale	7	0	7	0
Asset impairments	0	17	0	17
Net gain on insurance recovery for property damage	0	(6)	(2)	(6)
Equity in affiliates’ earnings, net of tax	(16)	(2)	(28)	(7)
Unrealized loss on equity securities	4	0	276	9
Interest income	(3)	(3)	(6)	(5)
Interest expense	42	18	63	30
Other postretirement income	(12)	(1)	(23)	(3)
Earnings (loss) before income taxes and noncontrolling interest	302	(90)	438	96
Provision (benefit) for income taxes	28	(6)	70	43
Net earnings (loss)	274	(84)	368	53
Net earnings attributable to noncontrolling interest, net of tax	27	14	56	22
Net earnings (loss) attributable to BorgWarner Inc.	247	(98)	312	31
Air Management
Segment Reporting Information
Segment Adjusted EBIT	277	28	599	236
Restructuring expense		16		29
e-Propulsion & Drivetrain
Segment Reporting Information
Segment Adjusted EBIT	132	1	269	64
Fuel Injection
Segment Reporting Information
Segment Adjusted EBIT	38	0	71	0
Aftermarket
Segment Reporting Information
Segment Adjusted EBIT	$ 32	$ 0	$ 53	$ 0