Supplemental Guarantor Condensed Consolidating Financial Statements - Condensed Consolidating Statement of Operations (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
	Mar. 13, 2020	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Condensed Income Statements, Captions [Line Items]
Sales		$ 871	$ 1,156	$ 1,772	$ 2,194
Cost of sales		(757)	(982)	(1,531)	(1,879)
GROSS PROFIT		114	174	241	315
Selling, general and administrative		(59)	(73)	(129)	(107)
Income from WABCO distribution termination	$ 265	265	0	265	0
Other operating income, net		(10)	1	(15)	1
OPERATING INCOME		310	102	362	209
Other income (expense), net		14	9	24	20
Equity in earnings of affiliates		6	6	12	15
Interest income (expense), net		(16)	(15)	(30)	(29)
INCOME BEFORE INCOME TAXES		314	102	368	215
Benefit (provision) for income taxes		(73)	(27)	(86)	(48)
Equity income from continuing operations of subsidiaries		0	0	0	0
INCOME FROM CONTINUING OPERATIONS		241	75	282	167
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax		1	(1)	1	(1)
NET INCOME		242	74	283	166
Less: Net income attributable to noncontrolling interests		(1)	(2)	(3)	(4)
Net income		241	72	280	162
External
Condensed Income Statements, Captions [Line Items]
Sales		871	1,156	1,772	2,194
Subsidiaries
Condensed Income Statements, Captions [Line Items]
Sales		0	0	0	0
Eliminations
Condensed Income Statements, Captions [Line Items]
Sales		(48)	(79)	(106)	(168)
Cost of sales		48	79	106	168
GROSS PROFIT		0	0	0	0
Selling, general and administrative		0	0	0	0
Income from WABCO distribution termination		0		0
Other operating income, net		0	0	0	0
OPERATING INCOME		0	0	0	0
Other income (expense), net		0	0	0	0
Equity in earnings of affiliates		0	0	0	0
Interest income (expense), net		0	0	0	0
INCOME BEFORE INCOME TAXES		0	0	0	0
Benefit (provision) for income taxes		0	0	0	0
Equity income from continuing operations of subsidiaries		(43)	(89)	(169)	(280)
INCOME FROM CONTINUING OPERATIONS		(43)	(89)	(169)	(280)
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax		(2)	0	(2)	0
NET INCOME		(45)	(89)	(171)	(280)
Less: Net income attributable to noncontrolling interests		0	0	0	0
Net income		(45)	(89)	(171)	(280)
Eliminations | External
Condensed Income Statements, Captions [Line Items]
Sales		0	0	0	0
Eliminations | Subsidiaries
Condensed Income Statements, Captions [Line Items]
Sales		(48)	(79)	(106)	(168)
Parent | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales		0	0	0	0
Cost of sales		(11)	(16)	(27)	(31)
GROSS PROFIT		(11)	(16)	(27)	(31)
Selling, general and administrative		(9)	(28)	(33)	(53)
Income from WABCO distribution termination		265		265
Other operating income, net		(1)	0	(1)	0
OPERATING INCOME		244	(44)	204	(84)
Other income (expense), net		44	50	44	50
Equity in earnings of affiliates		0	0	0	0
Interest income (expense), net		(31)	(33)	(62)	(65)
INCOME BEFORE INCOME TAXES		257	(27)	186	(99)
Benefit (provision) for income taxes		(58)	20	(46)	31
Equity income from continuing operations of subsidiaries		41	80	139	231
INCOME FROM CONTINUING OPERATIONS		240	73	279	163
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax		1	(1)	1	(1)
NET INCOME		241	72	280	162
Less: Net income attributable to noncontrolling interests		0	0	0	0
Net income		241	72	280	162
Parent | Reportable Legal Entities | External
Condensed Income Statements, Captions [Line Items]
Sales		0	0	0	0
Parent | Reportable Legal Entities | Subsidiaries
Condensed Income Statements, Captions [Line Items]
Sales		0	0	0	0
Guarantors | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales		536	705	1,094	1,326
Cost of sales		(461)	(590)	(930)	(1,124)
GROSS PROFIT		75	115	164	202
Selling, general and administrative		(33)	(30)	(62)	(57)
Income from WABCO distribution termination		0		0
Other operating income, net		(6)	0	(6)	0
OPERATING INCOME		36	85	96	145
Other income (expense), net		(9)	(14)	(2)	(9)
Equity in earnings of affiliates		5	3	9	10
Interest income (expense), net		9	12	20	24
INCOME BEFORE INCOME TAXES		41	86	123	170
Benefit (provision) for income taxes		(11)	(22)	(26)	(34)
Equity income from continuing operations of subsidiaries		2	9	30	49
INCOME FROM CONTINUING OPERATIONS		32	73	127	185
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax		1	0	1	0
NET INCOME		33	73	128	185
Less: Net income attributable to noncontrolling interests		0	0	0	0
Net income		33	73	128	185
Guarantors | Reportable Legal Entities | External
Condensed Income Statements, Captions [Line Items]
Sales		515	677	1,050	1,266
Guarantors | Reportable Legal Entities | Subsidiaries
Condensed Income Statements, Captions [Line Items]
Sales		21	28	44	60
Non- Guarantors | Reportable Legal Entities
Condensed Income Statements, Captions [Line Items]
Sales		383	530	784	1,036
Cost of sales		(333)	(455)	(680)	(892)
GROSS PROFIT		50	75	104	144
Selling, general and administrative		(17)	(15)	(34)	3
Income from WABCO distribution termination		0		0
Other operating income, net		(3)	1	(8)	1
OPERATING INCOME		30	61	62	148
Other income (expense), net		(21)	(27)	(18)	(21)
Equity in earnings of affiliates		1	3	3	5
Interest income (expense), net		6	6	12	12
INCOME BEFORE INCOME TAXES		16	43	59	144
Benefit (provision) for income taxes		(4)	(25)	(14)	(45)
Equity income from continuing operations of subsidiaries		0	0	0	0
INCOME FROM CONTINUING OPERATIONS		12	18	45	99
INCOME (LOSS) FROM DISCONTINUED OPERATIONS, net of tax		1	0	1	0
NET INCOME		13	18	46	99
Less: Net income attributable to noncontrolling interests		(1)	(2)	(3)	(4)
Net income		12	16	43	95
Non- Guarantors | Reportable Legal Entities | External
Condensed Income Statements, Captions [Line Items]
Sales		356	479	722	928
Non- Guarantors | Reportable Legal Entities | Subsidiaries
Condensed Income Statements, Captions [Line Items]
Sales		$ 27	$ 51	$ 62	$ 108