Derivative Financial Instruments - Effect on the Consolidated Statement of Comprehensive Income (Details) - Noninterest income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Interest rate swaps
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income	$ (21,925)	$ 18,946	$ (53,379)	$ (27,357)
Mortgage loan commitments
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income	201	(26)	253	1
Mortgage loan forward sale contracts
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Income	$ (201)	$ 26	$ (253)	$ (1)