Reporting Segments (Details) $ in Millions		3 Months Ended			6 Months Ended
		Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2018 USD ($) segment	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segment					2
Net Sales by Reporting Segment
Sales Revenue, Goods, Net		$ 2,694.0	$ 2,389.7		$ 5,478.3	$ 4,796.7
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT		395.1	352.5		796.3	703.1
Restructuring expense		31.2	0.0		38.7	0.0
Merger, acquisition and divestiture expense		1.0	0.0		3.2	0.0
Lease termination settlement		0.0	0.0	$ 5.3	0.0	5.3
Other income, net		0.0	0.0		(4.8)	0.0
Other postretirement income		(2.4)	(1.4)		(5.0)	(2.6)
Corporate, including equity in affiliates' earnings and stock-based compensation		37.1	40.0		89.7	84.1
Interest income		(1.4)	(1.4)		(2.9)	(2.9)
Interest expense and finance charges		14.9	18.0		31.0	36.0
Earnings before income taxes and noncontrolling interest		314.7	297.3		646.4	583.2
Provision for income taxes		30.4	76.2		125.3	162.5
Net earnings		284.3	221.1		521.1	420.7
Net earnings attributable to the noncontrolling interest, net of tax		12.5	9.1		24.2	19.5
Net earnings attributable to BorgWarner Inc.		271.8	212.0		496.9	401.2
Segment Reporting Information - Assets
Total assets		9,777.2			9,777.2		$ 9,787.6
Operating Segments [Member]
Segment Reporting Information - Assets
Total assets		8,662.6			8,662.6		8,636.7
Engine [Member]
Net Sales by Reporting Segment
Sales Revenue, Goods, Net		1,674.3	1,481.8		3,390.4	2,977.2
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT		278.8	243.3		559.0	489.5
Restructuring expense		28.1			32.9
Segment Reporting Information - Assets
Total assets		4,741.0			4,741.0		4,732.9
Drivetrain [Member]
Net Sales by Reporting Segment
Sales Revenue, Goods, Net		1,034.1	921.0		2,117.0	1,845.9
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT		116.3	109.2		237.3	213.6
Restructuring expense		3.2			5.5
Segment Reporting Information - Assets
Total assets		3,921.6			3,921.6		3,903.8
Intersegment Eliminations [Member]
Net Sales by Reporting Segment
Sales Revenue, Goods, Net		(14.4)	$ (13.1)		(29.1)	$ (26.4)
Corporate, Non-Segment [Member]
Segment Reporting Information - Assets
Total assets	[1]	$ 1,114.6			$ 1,114.6		$ 1,150.9

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