Derivative Financial Instruments - Offsetting Liabilities and Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Sep. 30, 2015
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative financial assets, gross amount	$ 525	$ 41
Derivative financial liabilities, gross amount	(81,974)	(53,559)
Derivative financial assets (liabilities), gross amount	(81,449)	(53,518)
Derivative financial assets, amount offset	(525)	(41)
Derivative financial liabilities, amount offset	525	41
Derivative financial assets (liabilities), Net, amount offset	0	0
Derivative financial assets, net amount presented in Consolidated Balance Sheets	0	0
Derivative financial liabilities, net amount presented in Consolidated Balance Sheets	(81,449)	(53,518)
Derivative financial assets (liabilities), net amount presented in Consolidated Balance Sheets	(81,449)	(53,518)
Derivative financial assets, Held/pledged financial instruments	0	0
Derivative financial liabilities, Held/pledged financial instruments	81,449	53,518
Derivative liabilities (assets), Net, Held/pledged financial instruments	81,449	53,518
Derivative financial asset, net amount	0	0
Derivative financial liabilities, net amount	0	0
Derivative financial assets (liabilities), net, amount offset against collateral	$ 0	$ 0