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Acquisition of NHUMO - Components and Allocation of Purchase Price (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended	6 Months Ended
	Nov. 30, 2013	Oct. 31, 2013	Mar. 31, 2015	Sep. 30, 2014
Assets
Goodwill			$ 508us-gaap_Goodwill	$ 536us-gaap_Goodwill
NHUMO [Member]
Assets
Current assets		54		54
Property, plant and equipment		48		48
Other non-current assets		1		1
Intangible assets		57		63
Goodwill		51		45
Total assets acquired		211		211
Liabilities
Accounts payable, accruals and other liabilities		(18)		(20)
Deferred tax liabilities - long-term		(31)		(29)
Total liabilities assumed		(49)		(49)
Net assets acquired		162		162
Cash consideration paid	(80)	80
Fair value of redeemable preferred stock		28
Previously held equity interest in NHUMO		54	(54)
Total		162
NHUMO [Member] \| Measurement Period Adjustments [Member]
Assets
Intangible assets				6
Goodwill				(6)
Liabilities
Accounts payable, accruals and other liabilities				(2)
Deferred tax liabilities - long-term				$ 2