Derivative Instruments and Hedging Activities - Additional Information (Detail)	3 Months Ended
	Dec. 31, 2014 USD ($) Swap	Dec. 31, 2013 USD ($) Swap	Sep. 30, 2013 USD ($)	Sep. 30, 2005 USD ($) Agreement	Sep. 30, 2014 USD ($) Swap	Dec. 31, 2013 JPY (¥)	Mar. 31, 2006 Agreement	Dec. 31, 2014 Cross-Currency Interest Rate Swaps JPY (¥) Swap	Sep. 30, 2014 Cross-Currency Interest Rate Swaps JPY (¥) Swap	Dec. 31, 2013 Cross-Currency Interest Rate Swaps JPY (¥) Swap	Dec. 31, 2014 Common stock shares USD ($)	Sep. 30, 2014 Common stock shares USD ($)	Dec. 31, 2013 Common stock shares USD ($)
Derivative [Line Items]
Hedge percentage for foreign exchange transactional exposures, Minimum	70.00%
Hedge percentage for foreign exchange transactional exposures, Maximum	90.00%
Cross-currency interest rate swaps outstanding						¥ 20,000,000,000		¥ 20,000,000,000	¥ 20,000,000,000	¥ 20,000,000,000
Types Of Notes Forward Treasury Lock Agreements Fixed Portion Of Future Interest Cost				5-year, 10-year and 30-year bonds
Derivative, Amount of Hedged Item											4,100,000	4,400,000	4,600,000
Number of fixed to floating interest rate swaps outstanding	13	10			13			4	4	4
Number of forward treasury lock agreements				3
Notional amount of forward treasury lock agreements, total				1,300,000,000
Number of forward treasury lock agreements terminated							3
Amount of gains (losses) recognized in CTA on the effective portion of outstanding net investment hedges	15,000,000	11,000,000			9,000,000
Gains (losses) reclassified from CTA to income for the Company's outstanding net investment hedges	0	0
Gains (losses) recognized in income for the ineffective portion of cash flow hedges	0	0
Increase (Decrease) in Cash Collateral for Loaned Securities	$ 0	$ 0	$ 0