Allowance for Loan and Lease Losses - Summary of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	$ 57,200	$ 47,518	$ 55,864
Charge-offs	(14,166)	(15,714)	(13,743)
Recoveries	4,653	6,355	4,713
Provision	18,011	19,718	4,456
Allowance for loan losses, ending balance	64,642	57,200	47,518
Receivables acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	2,776
(Improvement) impairment of ASC 310-30 loans	(1,056)	(677)	(3,772)
Allowance for loan losses, ending balance	1,679	2,776
Residential real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	8,025	8,342	11,779
Charge-offs	(1,157)	(238)	(631)
Recoveries	495	231	233
Provision	419	849	(788)
Allowance for loan losses, ending balance	7,106	8,025	8,342
Residential real estate \| Receivables acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	1,624
(Improvement) impairment of ASC 310-30 loans	(676)	(1,159)	(2,251)
Allowance for loan losses, ending balance	907	1,624
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	18,014	16,884	22,562
Charge-offs	(3,625)	(1,971)	(3,199)
Recoveries	719	1,339	1,470
Provision	3,148	1,325	(4,114)
Allowance for loan losses, ending balance	17,946	18,014	16,884
Commercial real estate \| Receivables acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	1,082
(Improvement) impairment of ASC 310-30 loans	(310)	437	165
Allowance for loan losses, ending balance	772	1,082
Commercial non real estate
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	15,996	10,550	11,222
Charge-offs	(2,629)	(11,153)	(5,380)
Recoveries	1,429	3,407	1,439
Provision	(1,736)	13,122	4,980
Allowance for loan losses, ending balance	12,990	15,996	10,550
Commercial non real estate \| Receivables acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	70
(Improvement) impairment of ASC 310-30 loans	(70)	70	(1,711)
Allowance for loan losses, ending balance	0	70
Agriculture
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	13,952	10,655	9,296
Charge-offs	(4,294)	(606)	(2,429)
Recoveries	556	131	58
Provision	14,901	3,772	3,730
Allowance for loan losses, ending balance	25,115	13,952	10,655
Agriculture \| Receivables acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	0
(Improvement) impairment of ASC 310-30 loans	0	0	0
Allowance for loan losses, ending balance	0	0
Consumer
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	348	264	312
Charge-offs	(206)	(129)	(211)
Recoveries	149	104	156
Provision	147	134	(18)
Allowance for loan losses, ending balance	438	348	264
Consumer \| Receivables acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	0
(Improvement) impairment of ASC 310-30 loans	0	(25)	25
Allowance for loan losses, ending balance	0	0
Other
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	865	823	693
Charge-offs	(2,255)	(1,617)	(1,893)
Recoveries	1,305	1,143	1,357
Provision	1,132	516	666
Allowance for loan losses, ending balance	1,047	865	823
Other \| Receivables acquired with deteriorated credit quality
Financing Receivable, Allowance for Credit Losses [Roll Forward]
Allowance for loan losses, beginning balance	0
(Improvement) impairment of ASC 310-30 loans	0	0	$ 0
Allowance for loan losses, ending balance	$ 0	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

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Amount, after recoveries, of loans and leases that have been written-off.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Amount of expense related to estimated loss from loan and lease transactions.

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