QUARTERLY FINANCIAL INFORMATION (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Quarterly Financial Information Disclosure [Abstract]
Sales	$ 853	$ 909	$ 864	$ 879	$ 933	$ 979	$ 954	$ 900	$ 3,505	$ 3,766	$ 3,672
Cost of sales	(745)	(785)	(749)	(764)	(793)	(855)	(836)	(795)	(3,043)	(3,279)	(3,277)
Gross margin	108	124	115	115	140	124	118	105	462	487	395
Provision for income taxes	18	(6)	(6)	(7)	0	(12)	(8)	(11)	(1)	(31)	(64)
Net income (loss)	(22)	14	43	30	4	234	3	13	65	254	(20)
Income (loss) from continuing operations attributable to Meritor, Inc.	(21)	15	39	32	29	237	1	12	65	279	(15)
NET INCOME (LOSS) ATTRIBUTABLE TO MERITOR, INC.	$ (21)	$ 13	$ 43	$ 29	$ 3	$ 234	$ 1	$ 11	$ 64	$ 249	$ (22)
Basic income (loss) per share from continuing operations	$ (0.22)	$ 0.15	$ 0.40	$ 0.33	$ 0.30	$ 2.43	$ 0.01	$ 0.12	$ 0.67	$ 2.86	$ (0.15)
Diluted income (loss) per share from continuing operations	$ (0.22)	$ 0.15	$ 0.38	$ 0.32	$ 0.29	$ 2.34	$ 0.01	$ 0.12	$ 0.65	$ 2.81	$ (0.15)