Financial Statements - Additional Information (Detail) $ in Millions	12 Months Ended
	Sep. 30, 2012 InterestInvestment Entity	Jun. 30, 2015 USD ($) Entity	Sep. 30, 2014 USD ($) Entity	Jun. 30, 2014 USD ($) Entity
Financial Statement Details [Line Items]
Number of VIEs where Company is Primary Beneficiary | Entity		3	3	3
Interest percentage minimum for investments in partially-owned affiliates to be accounted for by the equity method		20.00%
Number of separate investments a pre-existing VIE was reorganized into | Entity	3
Additional interests acquired | InterestInvestment	2
Third party debt agreement		$ 162
Loans to partially-owned affiliates		59
Floor guarantee		25
Number of VIEs in which Company was not primary beneficiary | Entity	2
Restricted cash and cash equivalents		2	$ 4	$ 21
Variable Interest Entity, Not Primary Beneficiary [Member]
Financial Statement Details [Line Items]
Investment balance of the Company's nonconsolidated VIEs		$ 62	$ 59	$ 58
Automotive Experience
Financial Statement Details [Line Items]
Number of VIEs where Company is Primary Beneficiary | Entity		2
Power Solutions
Financial Statement Details [Line Items]
Number of VIEs where Company is Primary Beneficiary | Entity		1