Restructuring - Summary of Restructuring Activity (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	6 Months Ended
	Mar. 31, 2014	Mar. 31, 2014
Restructuring Cost And Reserve [Line Items]
Beginning balance		$ 10
Restructuring expense	17	24
Cash Payments		(19)
Ending balance	15	15
Employee-related Costs
Restructuring Cost And Reserve [Line Items]
Beginning balance		10
Restructuring expense	15	22
Cash Payments		(17)
Ending balance	15	15
Real Estate Costs
Restructuring Cost And Reserve [Line Items]
Beginning balance
Restructuring expense	1	1
Cash Payments		(1)
Ending balance
Other Costs
Restructuring Cost And Reserve [Line Items]
Beginning balance
Restructuring expense	1	1
Cash Payments		(1)
Ending balance