Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Income tax (expense) benefit	$ (17,000,000)	$ 3,000,000
Statutory income tax rate	35.00%	35.00%
Income withholding taxes and foreign losses uncertain tax positions	$ 0	$ 10,000,000
Income withholding taxes and state income tax losses uncertain tax positions	0
Maximum
Income Tax Contingency [Line Items]
Decrease in uncertain tax position	$ 20,000,000