Reporting Segments and Related Information - Adjusted EBIT (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Segment Reporting Information [Line Items]
Adjusted EBIT									$ 1,445.5		$ 1,311.8		$ 1,218.5
Asset impairment and loss on divestiture					$ 20.6				71.0		127.1		0.0
Restructuring expense	$ 45.2	$ 13.3				$ 1.3	$ 19.2	$ 6.4	58.5		26.9		65.7
Merger and acquisition expense	3.6	6.4			4.8	5.9	7.2	5.8	10.0		23.7		21.8
Lease termination settlement				$ 5.3					5.3		0.0		0.0
Other expense, net									2.1		0.0		0.0
Asbestos-related charge									0.0		703.6		0.0
Intangible asset impairment									0.0		12.6		0.0
Contract expiration gain									0.0		(6.2)		0.0
Pension settlement loss									0.0		0.0		25.7
Gain on previously held equity interest									0.0		0.0		(10.8)
Corporate, including equity in affiliates' earnings and stock-based compensation									170.3		155.3		136.4
Interest income	(1.6)	(1.3)	$ (1.4)	(1.5)	(1.6)	(1.6)	(1.5)	(1.6)	(5.8)		(6.3)		(7.5)
Interest expense and finance charges	16.9	17.6	18.0	18.0	19.5	22.4	21.4	21.3	70.5		84.6		60.4
Earnings before income taxes and noncontrolling interest									1,063.6		190.5		926.8
Provision for income taxes	338.4	79.4	76.2	86.3	(183.1)	48.8	84.2	80.4	580.3		30.3		280.4
Net earnings	(132.0)	194.6	221.1	199.6	(281.5)	93.1	175.4	173.2	483.3		160.2		646.4
Net earnings attributable to the noncontrolling interest, net of tax	14.2	9.7	9.1	10.4	11.8	9.8	11.0	9.1	43.4	[1]	41.7	[1]	36.7	[1]
Net earnings attributable to BorgWarner Inc.	$ (146.2)	$ 184.9	$ 212.0	$ 189.2	$ (293.3)	$ 83.3	$ 164.4	$ 164.1	439.9		118.5		609.7
Engine [Member]
Segment Reporting Information [Line Items]
Adjusted EBIT									995.7		947.3		913.9
Restructuring expense									48.2
Drivetrain [Member]
Segment Reporting Information [Line Items]
Adjusted EBIT									449.8		$ 364.5		$ 304.6
Restructuring expense									$ 6.8

[1] *Net of income taxes.