FHLB Advances and Other Borrowings - Additional Information (Details)	12 Months Ended
Sep. 30, 2017
Federal Home Loan Bank of Des Moines
Federal Home Loan Bank, Advances, Branch of FHLB Bank [Line Items]
Federal home loan bank, percent of assets	48.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Name:	us-gaap_FederalHomeLoanBankAdvancesBranchOfFHLBBankLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration