Reporting Segments (Details) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Sep. 30, 2018 USD ($) segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment					2
Net Sales by Reporting Segment
Net sales		$ 2,478.5	$ 2,416.2		$ 7,956.8	$ 7,212.9
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT		345.8	348.7		1,142.1	1,051.8
Restructuring expense		5.7	13.3		44.4	13.3
Merger, acquisition and divestiture expense		1.6	6.4		4.8	6.4
Lease termination settlement		0.0	0.0	$ 5.3	0.0	5.3
Other expense (income), net		1.5	2.7		(3.3)	2.7
Other postretirement income		(2.4)	(1.3)		(7.4)	(3.9)
Corporate, including equity in affiliates' earnings and stock-based compensation		43.8	37.3		133.5	121.4
Interest income		(1.5)	(1.3)		(4.4)	(4.2)
Interest expense and finance charges		14.4	17.6		45.4	53.6
Earnings before income taxes and noncontrolling interest		282.7	274.0		929.1	857.2
Provision for income taxes		66.8	79.4		192.1	241.9
Net earnings		215.9	194.6		737.0	615.3
Net earnings attributable to the noncontrolling interest, net of tax		12.1	9.7		36.3	29.2
Net earnings attributable to BorgWarner Inc.		203.8	184.9		700.7	586.1
Segment Reporting Information - Assets
Total assets		9,716.4			9,716.4		$ 9,787.6
Operating Segments [Member]
Segment Reporting Information - Assets
Total assets		8,579.6			8,579.6		8,636.7
Engine [Member]
Net Sales by Reporting Segment
Net sales		1,515.8	1,506.4		4,906.2	4,483.6
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT		238.2	237.6		797.2	727.1
Restructuring expense		5.2	12.6		38.1
Segment Reporting Information - Assets
Total assets		4,757.7			4,757.7		4,732.9
Drivetrain [Member]
Net Sales by Reporting Segment
Net sales		976.7	921.8		3,093.7	2,767.7
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT		107.6	111.1		344.9	324.7
Restructuring expense		0.5	0.7		6.0
Segment Reporting Information - Assets
Total assets		3,821.9			3,821.9		3,903.8
Intersegment Eliminations [Member]
Net Sales by Reporting Segment
Net sales		(14.0)	$ (12.0)		(43.1)	$ (38.4)
Corporate, Non-Segment [Member]
Segment Reporting Information - Assets
Total assets	[1]	$ 1,136.8			$ 1,136.8		$ 1,150.9

[1] Corporate assets include investments and other long-term receivables and certain deferred income taxes.