Derivatives - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Sep. 30, 2016
Derivative [Line Items]
Gain on foreign currency translation adjustment	$ 56,000,000	$ 65,000,000	$ (69,000,000)	$ 18,000,000
Cross Currency Swaps [Member]
Derivative [Line Items]
Net investment hedge, ineffectiveness			0
Cross Currency Swaps [Member] | Prepaid Expenses And Other Asset Current And Non Current [Member]
Derivative [Line Items]
Fair value of swaps	7,000,000		7,000,000		$ 1,000,000
Cross Currency Swaps [Member] | Net Investment Hedge [Member]
Derivative [Line Items]
Notional amount					250,000,000
Net cash interest received	2,000,000
Gain on foreign currency translation adjustment	1,000,000		8,000,000
Cumulative gain related to swaps	$ 9,000,000		9,000,000		1,000,000
Gains or losses reclassified from accumulated other comprehensive income (loss) into earnings			$ 0		$ 0