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Short-Term Borrowings - Narrative (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Federal Funds Purchased |  |
Short-term borrowings |  |
Outstanding credit facility | $ 0.0 | $ 0.0
Unsecured maximum borrowing capacity | 87.0 | 87.0
Federal Home Loan Bank Advances |  |
Short-term borrowings |  |
Outstanding credit facility | $ 631.7 | 552.2
Unsecured Line Of Credit With Bank of North Dakota |  |
Short-term borrowings |  |
Unsecured maximum borrowing capacity |  | $ 15.0

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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 + Details
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