Earnings Per Share (Details) (USD $) In Millions, except Share data in Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Basic earnings per share:
Net earnings attributable to BorgWarner Inc.	$ 158.0	$ 124.5
Weighted average shares of common stock outstanding	108,420	110,634
Earnings per share - basic	$ 1.46	$ 1.13
Diluted earnings per share:
Net earnings attributable to BorgWarner Inc.	158.0	124.5
Adjustment for net interest expense on convertible notes	5.0	5.2
Diluted net earnings attributable to BorgWarner Inc.	$ 163.0	$ 129.7
Weighted average shares of common stock outstanding	108,420	110,634
Effect of 3.50% convertible notes	11,389	11,389
Effect of warrant	5,813	5,416
Effect of stock-based compensation	2,120	2,785
Total dilutive effect on weighted average shares of common stock outstanding	19,322	19,590
Weighted average shares of common stock outstanding including dilutive shares	127,742	130,224
Earnings per share - diluted	$ 1.28	$ 1.00
Debt Instrument, Interest Rate, Stated Percentage	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	6,650	6,312