Accumulated Other Comprehensive Income - Schedule of Accumulated Other Comprehensive Income (Loss) (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified into income	$ 10
Benefit Plans Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified into income	9	14
Unrealized Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amounts reclassified into income	$ 1	$ 1