Reporting Segments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			9 Months Ended			12 Months Ended
	Sep. 30, 2012		Sep. 30, 2011	Sep. 30, 2012		Sep. 30, 2011	Dec. 31, 2008	Dec. 31, 2011
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	$ 1,695.2		$ 1,791.8	$ 5,464.1		$ 5,341.0
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT	228.2		231.7	764.3		685.9
Loss from disposal activities	1.8		0	39.7		0
Restructuring Charges	27.4		0	27.4		0
Gain (Loss) Related to Litigation Settlement	0		0	0		(29.1)	4.0
Corporate, including equity in affiliates' earnings and stock-based compensation	24.9		21.4	82.2		80.6
Interest income	(1.0)		(1.3)	(3.7)		(3.5)
Interest expense and finance charges	5.0		18.5	32.7		57.4
Earnings before income taxes and noncontrolling interest	170.1		193.1	586.0		580.5
Provision for income taxes	64.2		46.4	190.2		137.1
Net earnings	105.9		146.7	395.8		443.4
Net earnings attributable to the noncontrolling interest, net of tax	4.8		5.1	16.1		15.3
Net earnings attributable to BorgWarner Inc.	101.1		141.6	379.7		428.1
Segment Reporting Information - Assets
Total assets	6,346.5			6,346.5				5,958.6
Operating Segments [Member]
Segment Reporting Information - Assets
Total assets	4,972.1			4,972.1				4,891.8
Engine [Member]
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	1,168.0		1,258.2	3,745.8		3,805.5
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT	184.1		188.2	604.4		571.5
Segment Reporting Information - Assets
Total assets	3,343.8			3,343.8				3,329.0
Drivetrain [Member]
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	534.4		538.7	1,739.7		1,550.8
Adjusted earnings before interest, income taxes and noncontrolling interest
Adjusted EBIT	44.1		43.5	159.9		114.4
Segment Reporting Information - Assets
Total assets	1,628.3			1,628.3				1,562.8
Intersegment Elimination [Member]
Net Sales by Reporting Segment
Segment Reporting, Entity Consolidated Revenue	(7.2)		(5.1)	(21.4)		(15.3)
Corporate [Member]
Segment Reporting Information - Assets
Total assets	$ 1,374.4	[1]		$ 1,374.4	[1]			$ 1,066.8	[1]

[1] Corporate assets include investments and advances and deferred income taxes