Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2011	Mar. 31, 2011	Jun. 30, 2010	Mar. 31, 2010	Jun. 30, 2011	Jun. 30, 2010
Basic earnings per share:
Net earnings attributable to BorgWarner Inc.	$ 162.0		$ 82.8		$ 286.5	$ 159.0
Weighted average shares of common stock outstanding	108,761,000		115,362,000		109,697,000	115,869,000
Earnings per share - basic	$ 1.49		$ 0.72		$ 2.61	$ 1.37
Diluted earnings per share:
Net earnings attributable to BorgWarner Inc.	162.0		82.8		286.5	159.0
Adjustment for net interest expense on convertible notes	5.4		5.1		10.6	10.1
Diluted net earnings attributable to BorgWarner Inc.	$ 167.4		$ 87.9		$ 297.1	$ 169.1
Weighted average shares of common stock outstanding	108,761,000		115,362,000		109,697,000	115,869,000
Effect of 3.50% convertible notes	11,389,000		11,389,000		11,389,000	11,389,000
Effect of warrant	5,421,000		118,000		5,419,000	59,000
Effect of stock-based compensation	2,571,000		2,209,000		2,678,000	2,055,000
Total dilutive effect on weighted average shares of common stock outstanding	19,381,000		13,716,000		19,486,000	13,503,000
Weighted average shares of common stock outstanding including dilutive shares	128,142,000		129,078,000		129,183,000	129,372,000
Earnings per share - diluted	$ 1.31		$ 0.68		$ 2.3	$ 1.31
Common stock - shares authorized	390,000,000				390,000,000
Common stock - shares outstanding	108,674,881				108,674,881
Debt Instrument, Interest Rate, Stated Percentage	3.50%			3.50%	3.50%
Warrant Exercise Price		$ 38.61			$ 38.61
Bond Hedge Per Share Price				$ 32.82	$ 32.82
Bond hedge [Member]
Diluted earnings per share:
Anti-dilutive securities	6,317,000		1,808,000		6,314,000	1,526,000