Debt - Schedule of Senior Unsecured Note Issued (Parenthetical) (Detail)	3 Months Ended
	Dec. 31, 2014
Floating Rate Notes due June 15, 2016 [Member]
Debt Instrument [Line Items]
Debt Instrument, Maturity Date	Jun. 15, 2016
1.800% Notes due December 15, 2017 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate	1.80%
Debt Instrument, Maturity Date	Dec. 15, 2017
2.675% Notes due December 15, 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate	2.675%
Debt Instrument, Maturity Date	Dec. 15, 2019
3.734% Notes due December 15, 2024 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate	3.734%
Debt Instrument, Maturity Date	Dec. 15, 2024
4.685% Notes due December 15, 2044 [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate	4.685%
Debt Instrument, Maturity Date	Dec. 15, 2044