CONDENSED CONSOLIDATED STATEMENT OF EQUITY - USD ($) $ in Millions	Total	Common Stock	Additional Paid-in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Loss	Total Equity Attributable to Meritor, Inc.	Noncontrolling Interests
Beginning balance at Sep. 30, 2018	$ 317	$ 102	$ 787	$ 200	$ (236)	$ (566)	$ 287	$ 30
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	171			162		4	166	5
Equity based compensation expense	8		8				8
Vesting of equity based awards	0	2	(2)
Repurchase of common stock	(50)				(50)		(50)
Noncontrolling interest dividends	(1)							(1)
Ending Balance at Mar. 31, 2019	445	104	793	362	(286)	(562)	411	34
Beginning balance at Dec. 31, 2018	362	104	790	290	(286)	(569)	329	33
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	81			72		7	79	2
Equity based compensation expense	3		3				3
Noncontrolling interest dividends	(1)							(1)
Ending Balance at Mar. 31, 2019	445	104	793	362	(286)	(562)	411	34
Beginning balance at Sep. 30, 2019	415	104	803	491	(332)	(681)	385	30
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	250			280		(33)	247	3
Equity based compensation expense	1		1				1
Vesting of equity based awards	0	1	(1)
Repurchase of common stock	(241)				(241)		(241)
Noncontrolling interest dividends	(1)							(1)
Ending Balance at Mar. 31, 2020	424	105	803	771	(573)	(714)	392	32
Beginning balance at Dec. 31, 2019	384	105	804	530	(432)	(655)	352	32
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Comprehensive income (loss)	183			241		(59)	182	1
Equity based compensation expense	(2)		(2)				(2)
Repurchase of common stock	(141)				(141)		(141)
Noncontrolling interest dividends	(1)							(1)
Other equity adjustments	1		1				1
Ending Balance at Mar. 31, 2020	$ 424	$ 105	$ 803	$ 771	$ (573)	$ (714)	$ 392	$ 32