CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income	$ 66	$ 242	$ 99	$ 283
Foreign currency translation adjustments:
Attributable to Meritor, Inc.	(22)	(56)	33	(35)
Attributable to noncontrolling interests	(1)	0	0	0
Pension and other postretirement benefit related adjustments	2	2	5	5
Unrealized gain (loss) on cash flow hedges	0	(5)	1	(3)
Other comprehensive income (loss), net of tax	(21)	(59)	39	(33)
Total comprehensive income	45	183	138	250
Less: Comprehensive income attributable to noncontrolling interests	(2)	(1)	(4)	(3)
Comprehensive income attributable to Meritor, Inc.	$ 43	$ 182	$ 134	$ 247