Derivative Instruments and Hedging Activities - Additional Information (Detail) ¥ in Billions	3 Months Ended			9 Months Ended
	Jun. 30, 2015 USD ($) Swap	Jun. 30, 2014 USD ($) Swap	Sep. 30, 2005 USD ($) Agreement	Jun. 30, 2015 USD ($) Swap	Jun. 30, 2014 USD ($) Swap	Jun. 30, 2015 JPY (¥) Swap	Sep. 30, 2014 USD ($) Swap	Sep. 30, 2014 JPY (¥) Swap	Jun. 30, 2014 JPY (¥) Swap	Mar. 31, 2006 Agreement
Derivative [Line Items]
Hedge percentage for foreign exchange transactional exposures, Minimum				70.00%
Hedge percentage for foreign exchange transactional exposures, Maximum				90.00%
Number of fixed to floating interest rate swaps outstanding | Swap	12	13		12	13	12	13	13	13
Number of forward treasury lock agreements | Agreement			3
Notional amount of forward treasury lock agreements, total			$ 1,300,000,000
Types Of Notes Forward Treasury Lock Agreements Fixed Portion Of Future Interest Cost			5-year, 10-year and 30-year bonds
Number of forward treasury lock agreements terminated | Agreement										3
Collateral posted	$ 0	$ 0		$ 0	$ 0		$ 0
Amount of gains (losses) recognized in CTA on the effective portion of outstanding net investment hedges	10,000,000	2,000,000		10,000,000	2,000,000		$ 9,000,000
Gains (losses) reclassified from CTA to income for the Company's outstanding net investment hedges	0	0		0	0
Gains (losses) recognized in income for the ineffective portion of cash flow hedges	$ 0	$ 0		$ 0	$ 0
Cross-Currency Interest Rate Swaps
Derivative [Line Items]
Number of fixed to floating interest rate swaps outstanding | Swap	4	4		4	4	4	4	4	4
Cross-currency interest rate swaps outstanding | ¥						¥ 20		¥ 20	¥ 20
Common stock shares
Derivative [Line Items]
Derivative, Amount of Hedged Item	$ 4,000,000	$ 4,600,000		$ 4,000,000	$ 4,600,000		$ 4,400,000