CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (34)	$ 16
Foreign currency translation adjustments:
Attributable to Meritor, Inc.	(8)	(28)
Attributable to noncontrolling interest	1	(2)
Pension and other postretirement benefit related adjustments	3	11
Unrealized gain on investments and foreign exchange contracts	0	1
Other comprehensive loss, net of tax	(4)	(18)
Total comprehensive income (loss)	(38)	(2)
Less: Comprehensive (income) loss attributable to noncontrolling interest	(3)	1
Comprehensive income (loss) attributable to Meritor, Inc.	$ (41)	$ (1)