Accumulated Other Comprehensive Income (Loss) (Tables)

6 Months Ended

Mar. 31, 2017

Changes in Each Component of AOCI, Net of Tax

Changes in each component of AOCI, net of tax, were as follows:

	Currency Translation Adjustment			Unrealized Gains on Investments		Pension and Other Postretirement Benefit Liability Adjustments			Total
	(In millions)
Balance at September 30, 2016, attributable to Cabot Corporation	$	(227	)	$	2	$	(100	)	$	(325	)
Other comprehensive income (loss)		(125	)		—		1			(124	)
Net other comprehensive items		(352	)		2		(99	)		(449	)
Less: Noncontrolling interest		(4	)		—		—			(4	)
Balance at December 31, 2016, attributable to Cabot Corporation		(348	)		2		(99	)		(445	)
Other comprehensive income (loss)		56			—		1			57
Net other comprehensive items		(292	)		2		(98	)		(388	)
Less: Noncontrolling interest		1			—		—			1
Balance at March 31, 2017, attributable to Cabot Corporation	$	(293	)	$	2	$	(98	)	$	(389	)

Amounts Reclassified Out of AOCI

The amounts reclassified out of AOCI and into the Consolidated Statements of Operations in the three and six months ended March 31, 2017 and 2016 were as follows:

		Three Months Ended						Six Months Ended
	Affected Line Item in the Consolidated	March 31,						March 31,
	Statements of Operations	2017			2016			2017			2016
		(In millions)
Pension and other postretirement benefit liability adjustment
Amortization of actuarial losses	Net Periodic Benefit Cost - see Note C for details	$	2		$	1		$	3		$	2
Amortization of prior service credit	Net Periodic Benefit Cost - see Note C for details		(1	)		(1	)		(1	)		(2	)
Settlement and curtailment (credit) cost	Net Periodic Benefit Cost - see Note C for details		—			—			—			(1	)
Total before tax			1			—			2			(1	)
Tax impact	Provision (benefit) for income taxes		—			1			—			1
Total after tax		$	1		$	1		$	2		$	—