Accumulated Other Comprehensive Income (Loss)

12 Months Ended

Sep. 30, 2016

Stockholders Equity Note [Abstract]

Accumulated Other Comprehensive Income (Loss)

Note Q. Accumulated Other Comprehensive Income (Loss)

Changes in each component of Accumulated other comprehensive income (loss), net of tax, are as follows for fiscal 2015 and 2016:

	Currency Translation Adjustment			Unrealized Gains on Investment		Pension and Other Postretirement Benefit Liability Adjustment			Total
	(Dollars in millions)
Balance at September 30, 2014 attributable to    Cabot Corporation	$	27		$	2	$	(93	)	$	(64	)
Other comprehensive income (loss) before reclassifications		(270	)		—		7			(263	)
Amounts reclassified from accumulated other    comprehensive income		—			—		24			24
Net other comprehensive items		(243	)		2		(62	)		(303	)
Less: Noncontrolling interest		(4	)		—		—			(4	)
Balance at September 30, 2015 attributable to    Cabot Corporation		(239	)		2		(62	)		(299	)
Other comprehensive income (loss) before reclassifications		7			—		(38	)		(31	)
Amounts reclassified from accumulated other    comprehensive income		—			—		—			—
Net other comprehensive items		(232	)		2		(100	)		(330	)
Less: Noncontrolling interest		(5	)		—		—			(5	)
Balance at September 30, 2016 attributable to    Cabot Corporation	$	(227	)	$	2	$	(100	)	$	(325	)

The amounts reclassified out of Accumulated other comprehensive income (loss) and into the Statements of Operations for the fiscal year ended September 30, 2016, 2015 and 2014 are as follows:

	Affected Line Item in the Consolidated	September 30
	Statements of Operations	2016			2015			2014
		(Dollars in Millions)
Pension and other postretirement benefit    liability adjustment
Amortization of actuarial losses (gains)	Net Periodic Benefit Cost - see Note N for details	$	3		$	(1	)	$	3
Amortization of prior service (credit) cost	Net Periodic Benefit Cost - see Note N for details		(3	)		4			(3	)
Settlement costs	Net Periodic Benefit Cost - see Note N for details		—			27			—
Total before tax			—			30			—
Tax impact	Provision for income taxes		—			(6	)		—
Total after tax		$	—		$	24		$	—