The Fair Value Option For Certain Loans - Schedule of Fair Value Option (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net increase in fair value of loans at fair value	$ 26,314	$ 36,742	$ 11,904
Long-term loans and written loan commitments
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net increase in fair value of loans at fair value	26,314	36,742	11,904
Long-term loans and written loan commitments | Noninterest Income
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Net increase in fair value of loans at fair value	$ 26,314	$ 36,742	$ 11,904