Schedule of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Sep. 30, 2016
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Derivative contracts designated as hedging instruments, Assets	$ 7,400	$ 2,948
Derivative contracts not designated as hedging instruments, Assets	515	143
Embedded derivatives, Assets	1,009	2,485
Derivative contracts designated as hedging instruments, Liabilities	676	7,828
Derivative contracts not designated as hedging instruments, Liabilities	3,840	6,720
Embedded derivatives, Liabilities	1,287	985
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated value of assets held for sale	14,125	26,850
Estimated value of liabilities held for sale	$ 2,156	$ 11,133