Reporting Segments (Details) (USD $) In Millions	3 Months Ended			6 Months Ended			12 Months Ended
	Jun. 30, 2011		Jun. 30, 2010	Jun. 30, 2011		Jun. 30, 2010	Dec. 31, 2008	Dec. 31, 2010
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	$ 1,818.8		$ 1,421.7	$ 3,549.2		$ 2,708.5
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT	228.3		117.3	407.6		223.9
Adjusted EBIT	236.1		170.1	454.2		313.5
Patent infringement settlement	(29.1)		0	(29.1)		0	(4.0)
Environmental litigation settlement	0		28.0	0		28.0
BERU - Eichenauer equity investment gain	0		(8.0)	0		(8.0)
Corporate, including equity in affiliates' earnings and stock-based compensation	28.8		22.8	59.2		50.3
Interest income	(1.2)		(0.6)	(2.2)		(1.2)
Interest expense and finance charges	20.5		14.2	38.9		28.4
Earnings before income taxes and noncontrolling interest	217.1		113.7	387.4		216.0
Provision for income taxes	(49.8)		(26.0)	(90.7)		(46.9)
Net earnings	167.3		87.7	296.7		169.1
Net earnings attributable to the noncontrolling interest, net of tax	(5.3)		(4.9)	(10.2)		(10.1)
Net earnings attributable to BorgWarner Inc.	162.0		82.8	286.5		159.0
Segment Reporting Information - Assets
Total assets	6,226.0			6,226.0				5,555.0
Operating Segments [Member]
Segment Reporting Information - Assets
Total assets	5,181.1			5,181.1				4,508.2
Engine [Member]
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	1,297.9		1,017.6	2,547.3		1,923.6
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT	197.2		132.8	383.3		239.5
Segment Reporting Information - Assets
Total assets	3,566.2			3,566.2				3,277.7
Drivetrain [Member]
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	525.7		408.7	1,012.1		794.5
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT	38.9		37.3	70.9		74.0
Segment Reporting Information - Assets
Total assets	1,614.9			1,614.9				1,230.5
Business Intersegment, Eliminations [Member]
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	(4.8)		(4.6)	(10.2)		(9.6)
Corporate [Member]
Segment Reporting Information - Assets
Total assets	$ 1,044.9	[1]		$ 1,044.9	[1]			$ 1,046.8	[1]

[1] Corporate assets include equity in affiliates, investments and advances and deferred income taxes.