Acquisition Activity - Schedule of Pro Forma Information (Details) - HF Financial Corporation - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Net interest income	$ 98,642	$ 95,443
Net income	$ 36,903	$ 31,939
Basic earnings per share (in USD per share)	$ 0.63	$ 0.58
Fully diluted earnings per share (in USD per share)	$ 0.63	$ 0.58

Business Acquisition, Pro Forma Interest Income (Expense), Net

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- Definition

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.

+ References

No definition available.

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- Definition

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(2)-(3)
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

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- Definition

The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

+ References

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