Derivatives and Hedging Activities (Details) - USD ($)	3 Months Ended
	Dec. 31, 2016	Sep. 30, 2016
Derivative [Line Items]
Gain (loss) on derivative instruments	$ 0
Derivative asset, fair value, gross asset	2,560,000	$ 20,895,000
Derivative liability, fair value, gross liability	4,685,000	55,554,000
Interest rate swap agreements
Derivative [Line Items]
Customer derivatives program	878,860,000	840,935,000
Notional amount	700,000,000	700,000,000
Commercial loan interest rate swap
Derivative [Line Items]
Notional amount	52,936,000	54,155,000
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	2,076,000	31,347,000
Interest rate contracts | Other assets
Derivative [Line Items]
Derivative asset, fair value, gross asset	2,560,000	20,895,000
Interest rate contracts | Other liabilities
Derivative [Line Items]
Derivative liability, fair value, gross liability	2,560,000	20,895,000
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	$ 49,000	$ 3,312,000