Reporting Segments and Related Information - Adjusted EBIT (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended																12 Months Ended
	Dec. 31, 2011		Sep. 30, 2011		Jun. 30, 2011		Mar. 31, 2011		Dec. 31, 2010		Sep. 30, 2010		Jun. 30, 2010		Mar. 31, 2010		Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Reporting Information [Line Items]
Adjusted EBIT																	$ 935.5		$ 674.9		$ 206.3
Patent infringement settlement, net of legal costs incurred																	29.1		0		0
Loss on disposals																	(21.5)		0		0
Environmental litigation settlement																	0		28.0		0
BERU - Eichenauer investment gain																	0		(8.0)		0
Muncie closure retiree obligation net gain																	0		0		(27.9)
Corporate, including equity in affiliates' earnings and stock-based compensation																	(107.4)		(111.0)		(111.3)
Interest income	1.3		1.3		1.2		1.0		1.0		0.6		0.6		0.6		4.8		2.8		2.5
Interest expense and finance charges	17.2		18.5		20.5		18.4		22.0		18.4		14.2		14.2		74.6		68.8		57.2
Earnings before income taxes and noncontrolling interest	185.4		193.1		217.1		170.3		146.2		115.7		113.7		102.3		765.9		477.9		17.9
Provision (benefit) for income taxes	58.2		46.4		49.8		40.9		30.6		4.2		26.0		20.9		195.3		81.7		(18.5)
Net earnings	127.2		146.7		167.3		129.4		115.6		111.5		87.7		81.4		570.6		396.2		36.4
Net earnings attributable to the noncontrolling interest, net of tax	5.2		5.1		5.3		4.9		3.9		4.8		4.9		5.2		20.5		18.8		9.4
Net earnings attributable to BorgWarner Inc.	122.0	[1]	141.6	[1]	162.0	[1]	124.5	[1]	111.7	[1]	106.7	[1]	82.8	[1]	76.2	[1]	550.1	[1]	377.4	[1]	27.0
Engine [Member]
Segment Reporting Information [Line Items]
Adjusted EBIT																	774.3		537.9		219.8
Drivetrain [Member]
Segment Reporting Information [Line Items]
Adjusted EBIT																	$ 161.2		$ 137.0		$ (13.5)

[1] The Company's results were impacted by the following:•Quarter ended December 31, 2011: The Company incurred $21.5 million in expense associated with the loss on sale of the tire pressure monitoring business, including costs related to the divestiture, and a write-down of a portion of the ignitor and electronic business. The Company recorded $1.4 million of tax benefit associated with the disposals and $4.1 million of tax expense related to an intercompany disposal transaction.•Quarter ended June 30, 2011: The Company recorded a $29.1 million patent infringement settlement gain, net of legal costs incurred, which was partially offset by $11.0 million of additional tax expense. Additionally, the Company recorded a $6.2 million related to tax adjustments resulting from a change in state corporate income tax legislation as well as an adjustment of the Company's tax accounts as a result of the closure of certain tax audits.•Quarter ended September 30, 2010: The Company recorded a $21.2 million foreign tax credit valuation allowance reversal.•Quarter ended June 30, 2010: The Company recorded an $8.0 million BERU-Eichenauer Equity investment gain and $28.0 million environmental litigation settlement.•Quarter ended March 31, 2010: The Company recorded a $2.5 million Medicare Part D tax adjustment.