Interim Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Net sales	$ 2,572.8	$ 2,478.5	$ 2,694.0	$ 2,784.3	$ 2,586.4	$ 2,416.2	$ 2,389.7	$ 2,407.0	$ 10,529.6	$ 9,799.3	$ 9,071.0
Cost of sales	2,030.0	1,962.9	2,114.8	2,192.5	2,021.6	1,894.6	1,876.8	1,890.7	8,300.2	7,683.7	7,142.3
Gross profit	542.8	515.6	579.2	591.8	564.8	521.6	512.9	516.3	2,229.4	2,115.6	1,928.7
Selling, general and administrative expenses	225.8	230.5	236.0	253.4	240.0	225.0	215.1	219.0	945.7	899.1	818.0
Other expense, net	51.4	7.1	30.4	4.9	117.0	22.0	(0.3)	5.8	93.8	144.5	137.5
Operating income	265.6	278.0	312.8	333.5	207.8	274.6	298.1	291.5	1,189.9	1,072.0	973.2
Equity in affiliates’ earnings, net of tax	(10.5)	(15.2)	(13.0)	(10.2)	(12.7)	(14.4)	(14.4)	(9.7)	(48.9)	(51.2)	(42.9)
Interest income	(2.0)	(1.5)	(1.4)	(1.5)	(1.6)	(1.3)	(1.4)	(1.5)	(6.4)	(5.8)	(6.3)
Interest expense and finance charges	13.3	14.4	14.9	16.1	16.9	17.6	18.0	18.0	58.7	70.5	84.6
Other postretirement income	(2.0)	(2.4)	(2.4)	(2.6)	(1.2)	(1.3)	(1.4)	(1.2)	(9.4)	(5.1)	(4.9)
Earnings before income taxes and noncontrolling interest	266.8	282.7	314.7	331.7	206.4	274.0	297.3	285.9	1,195.9	1,063.6	942.7
Provision for income taxes	19.2	66.8	30.4	94.9	338.4	79.4	76.2	86.3	211.3	580.3	306.0
Net earnings (loss)	247.6	215.9	284.3	236.8	(132.0)	194.6	221.1	199.6	984.6	483.3	636.7
Net earnings attributable to the noncontrolling interest, net of tax	17.6	12.1	12.5	11.7	14.2	9.7	9.1	10.4	53.9	43.4	41.7
Net earnings attributable to BorgWarner Inc.	$ 230.0	$ 203.8	$ 271.8	$ 225.1	$ (146.2)	$ 184.9	$ 212.0	$ 189.2	$ 930.7	$ 439.9	$ 595.0
Earnings per share — basic	$ 1.11	$ 0.98	$ 1.30	$ 1.07	$ (0.70)	$ 0.88	$ 1.01	$ 0.89	$ 4.47	$ 2.09	$ 2.78
Earnings per share — diluted	$ 1.10	$ 0.98	$ 1.30	$ 1.07	$ (0.70)	$ 0.88	$ 1.00	$ 0.89	$ 4.44	$ 2.08	$ 2.76
Restructuring expense	$ 22.7	$ 5.7	$ 31.2	$ 7.5	$ 45.2	$ 13.3			$ 67.1	$ 58.5	$ 26.9
Gain on sale of building	19.4								19.4	0.0	0.0
Merger, acquisition and divestiture expense	1.0	1.6	1.0	2.2	3.6	6.4			5.8	10.0	23.7
Asset impairment expense	25.6				71.0				25.6	71.0	127.1
Asbestos-related adjustments	22.8								22.8	0.0	(48.6)
Lease termination settlement								$ 5.3	0.0	5.3	0.0
Tax benefit associated with restructuring	(5.5)	(1.3)	(7.6)	(0.6)	(8.9)	(1.2)			(15.0)	(10.1)	(6.0)
Effective rate reconciliation, measurement period adjustments due to the Tax Act	7.4	(6.6)	(13.4)						(12.6)
Tax expense on other expense	0.4
Effective Income Tax Rate Reconciliation, Deduction, Other, Amount		(0.4)
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	(0.4)	(0.5)	(21.1)						(22.0)
Valuation allowance adjustments	(9.1)								(10.6)	12.2	(2.7)
Effective income tax rate reconciliation, tax reserve adjustments	(2.8)								(2.8)
Effective Income Tax Rate Reconciliation, Disposition of Asset, Amount	5.8								5.8
Tax benefit associated with merger and acquisition expense	(0.1)			(0.3)	(0.7)	(0.3)			(0.3)	(1.0)
Tax benefit associated with asset impairment expense	(7.7)				(18.2)				(7.7)	(18.2)
Tax impact of other tax adjustments	(18.5)	(1.8)	$ (9.9)	0.4	7.9	$ (5.1)	$ (3.2)	$ 3.4	(29.8)	(3.8)	(8.6)
Tax expense on Merger and acquisition		$ 0.1
Tax expenses (benefits) associated with asbestos-related adjustments	$ (5.5)								(5.5)		17.5
Tax reform adjustments to provision for income taxes					$ 273.5				(12.6)	273.5	0.0
Tax expense on gain from customer contract expiration				0.9					0.9		2.2
Gain on commercial settlement				$ 4.0					$ 4.0	$ 0.0	$ 0.0