Derivatives and Hedging Activities (Details) - USD ($)	6 Months Ended
	Mar. 31, 2016	Sep. 30, 2015
Derivative [Line Items]
Gain (loss) on derivative instruments	$ 0
Derivative asset, fair value, gross asset	17,498,000	$ 11,879,000
Derivative liability, fair value, gross liability	45,069,000	27,400,000
Interest rate swap agreements
Derivative [Line Items]
Customer derivatives program	525,465,000	439,416,000
Notional amount	54,155,000	54,815,000
Interest rate contracts | Other assets
Derivative [Line Items]
Derivative asset, fair value, gross asset	17,498,000	11,879,000
Interest rate contracts | Other liabilities
Derivative [Line Items]
Derivative liability, fair value, gross liability	17,498,000	11,879,000
Commercial loan hedge | Other assets
Derivative [Line Items]
Derivative asset, fair value, gross asset	0	0
Commercial loan hedge | Other liabilities
Derivative [Line Items]
Derivative liability, fair value, gross liability	2,329,000	966,000
Long term borrowing hedge | Other assets
Derivative [Line Items]
Derivative asset, fair value, gross asset	0	0
Long term borrowing hedge | Other liabilities
Derivative [Line Items]
Derivative liability, fair value, gross liability	25,242,000	14,555,000
Forward Contracts | Interest rate swap agreements
Derivative [Line Items]
Notional amount	$ 600,000,000	$ 400,000,000