Earnings Per Share (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Basic earnings per share:
Net earnings attributable to BorgWarner Inc.	$ 141.6	$ 106.7	$ 428.1	$ 265.7
Weighted average shares of common stock outstanding	108,779,000	112,757,000	109,391,000	114,831,000
Earnings per share - basic	$ 1.3	$ 0.95	$ 3.91	$ 2.31
Diluted earnings per share:
Net earnings attributable to BorgWarner Inc.	141.6	106.7	428.1	265.7
Adjustment for net interest expense on convertible notes	5.4	5.0	16.0	15.1
Diluted net earnings attributable to BorgWarner Inc.	$ 147.0	$ 111.7	$ 444.1	$ 280.8
Weighted average shares of common stock outstanding	108,779,000	112,757,000	109,391,000	114,831,000
Effect of 3.50% convertible notes	11,389,000	11,389,000	11,389,000	11,389,000
Effect of warrant	5,158,000	1,596,000	5,332,000	584,000
Effect of stock-based compensation	2,614,000	2,062,000	2,657,000	1,731,000
Total dilutive effect on weighted average shares of common stock outstanding	19,161,000	15,047,000	19,378,000	13,704,000
Weighted average shares of common stock outstanding including dilutive shares	127,940,000	127,804,000	128,769,000	128,535,000
Earnings per share - diluted	$ 1.15	$ 0.87	$ 3.45	$ 2.18
Common stock - shares authorized	390,000,000		390,000,000
Common stock - shares outstanding	109,720,466		109,720,466
Debt Instrument, Interest Rate, Stated Percentage	3.50%	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	6,092,000	3,064,000	6,240,000	2,037,000