DOCUMENT AND ENTITY INFORMATION - shares	3 Months Ended
	Dec. 31, 2018	Jan. 28, 2019
Document and Entity Information [Abstract]
Entity registrant name	MERITOR INC
Entity central index key	0001113256
Current fiscal year end date	--09-30
Entity filer category	Large Accelerated Filer
Trading symbol	MTOR
Entity common stock, shares outstanding		83,385,576
Document period end date	Dec. 31, 2018
Document fiscal year focus	2019
Document type	10-Q
Document fiscal period focus	Q1
Entity emerging growth company	false
Entity small business	false
Amendment flag	false