Unaudited Quarterly Financial Information (Tables)

12 Months Ended

Sep. 30, 2020

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

Unaudited financial results by quarter for fiscal 2020 and 2019 are summarized below:

	Quarters Ended											Year Ended
	December 31,		March 31,			June 30,			September 30,			September 30,
	2019		2020			2020			2020			2020
	(In millions, except per share amounts)
Net sales and other operating revenues	$	727	$	710		$	518		$	659		$	2,614
Gross profit	$	141	$	153		$	69		$	137		$	500
Net income (loss)	$	46	$	3		$	(5	)	$	(265	)	$	(221	)
Net income (loss) attributable to Cabot    Corporation	$	41	$	(1	)	$	(6	)	$	(272	)	$	(238	)
Earnings per common share—basic	$	0.71	$	(0.01	)	$	(0.12	)	$	(4.81	)	$	(4.21	)
Earnings per common share—diluted	$	0.70	$	(0.01	)	$	(0.12	)	$	(4.81	)	$	(4.21	)

	Quarters Ended								Year Ended
	December 31,		March 31,		June 30,		September 30,		September 30,
	2018		2019		2019		2019		2019
	(In millions, except per share amounts)
Net sales and other operating revenues	$	821	$	844	$	845	$	827	$	3,337
Gross profit	$	166	$	178	$	170	$	171	$	685
Net income (loss)	$	77	$	29	$	40	$	40	$	186
Net income (loss) attributable to Cabot    Corporation	$	69	$	23	$	32	$	33	$	157
Earnings per common share—basic	$	1.14	$	0.39	$	0.55	$	0.56	$	2.64
Earnings per common share—diluted	$	1.14	$	0.39	$	0.55	$	0.55	$	2.63