REPORTING SEGMENTS AND RELATED INFORMATION - Adjusted EBIT (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Adjusted EBIT			$ 1,182	$ 1,438	$ 1,515
Corporate, including stock-based compensation			192	206	219
Restructuring expense		$ 50	203	72	67
Merger, acquisition and divestiture expense			96	11	6
Intangible asset accelerated amortization			38	0	0
Amortization of inventory fair value adjustment			27	0	0
Asset impairment and loss on divestiture			17	7	25
Net gain on insurance recovery for property damage			(9)	0	0
Gain on derecognition of subsidiary			0	(177)	0
Unfavorable arbitration loss			0	14	0
Officer stock awards modification			0	2	8
Asbestos-related adjustments			0	0	23
Gain on sale of building			0	0	(19)
Other operating income			0	0	(4)
Equity in affiliates' earnings, net of tax			18	32	49
Unrealized gain on equity securities			382	0	0
Interest income			(12)	(12)	(6)
Interest expense			73	55	59
Other postretirement (income) expense			(7)	27	(10)
Earnings before income taxes and noncontrolling interest			964	1,265	1,196
Provision for income taxes			397	468	211
Net earnings			567	797	985
Net earnings attributable to the noncontrolling interest, net of tax	[1]		67	51	54
Net earnings attributable to BorgWarner Inc.			500	746	931
Air Management
Segment Reporting Information [Line Items]
Adjusted EBIT			762	995	1,040
Asset impairment and loss on divestiture			9
e-Propulsion & Drivetrain
Segment Reporting Information [Line Items]
Adjusted EBIT			359	443	475
Restructuring expense					10
Asset impairment and loss on divestiture			8
Fuel Injection
Segment Reporting Information [Line Items]
Adjusted EBIT			39	0	0
Aftermarket
Segment Reporting Information [Line Items]
Adjusted EBIT			$ 22	$ 0	$ 0

[1] Net of income taxes.