Condensed Consolidated Statements of Comprehensive Income (Loss) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Statement of Other Comprehensive Income [Abstract]
Net earnings attributable to BorgWarner Inc.	$ 101.1	$ 141.6	$ 379.7	$ 428.1
Foreign currency translation adjustments
Foreign currency translation gain (loss) arising during period,	47.4	(147.5)	1.5	(16.2)
Foreign currency loss reclassified into earnings related to disposal activities	16.8	0	16.8	0
Foreign currency translation adjustments	64.2	(147.5)	18.3	(16.2)
Hedge instrument adjustments
Market value change of hedge instruments	3.1	(4.4)	16.8	(19.7)
Income taxes associated with the market value change of hedge instruments	(0.6)	1.1	(4.9)	5.5
Hedge instrument adjustments - (Gain) loss reclassified into net earnings	(9.0)	0.6	(6.4)	1.4
Hedge instruments adjustments - Income taxes reclassified into net earnings	2.8	(0.4)	1.8	(0.9)
Net change in hedge instruments	(3.7)	(3.1)	7.3	(13.7)
Defined benefit post employment plans
Defined benefit post employment plans - Net unrecognized loss arising during the period	0	0	(0.7)	0
Defined benefit post employment plans - Income taxes associated with net unrecognized loss arising during the period	0	0	0.3	0
Defined benefit post employment plans - Amortization of prior service benefit and unrecognized loss into net earnings	2.4	2.0	6.8	5.8
Defined benefit post employment plans - Income taxes reclassified into net earnings	(0.9)	(0.7)	(2.3)	(2.0)
Defined benefit post employment plans - Acquisition	0	0	0	(5.4)
Defined benefit post employment plans - Income taxes associated with acquisition	0	0	0	1.4
Net change in defined benefit post employment plans	1.5	1.3	4.1	(0.2)
Other changes in comprehensive income, net of tax	0	0	0.5	0.2
Comprehensive income (loss)	163.1	(7.7)	409.9	398.2
Comprehensive income (loss) attributable to noncontrolling interest	1.3	(4.1)	1.4	(1.4)
Comprehensive income (loss) attributable to BorgWarner Inc.	$ 164.4	$ (11.8)	$ 411.3	$ 396.8