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v3.25.2

Commitments and Contingencies Commitments (Details) $ in Thousands | Jun. 30, 2025 USD ($)
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Lending related commitments [Line Items] |
Unused Commitments to Extend Credit | $ 5,590,367
Commitments to fund loans |
Lending related commitments [Line Items] |
Unused Commitments to Extend Credit | 344,523
Unfunded commitments under lines of credit |
Lending related commitments [Line Items] |
Unused Commitments to Extend Credit | 5,055,476
Commercial and standby letters of credit |
Lending related commitments [Line Items] |
Unused Commitments to Extend Credit | $ 190,368

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- Definition [Line Items] for Lending related commitments [Table] + References No definition available. + Details
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Namespace Prefix: | bku_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Unused amount of commitments to extend credit to customers. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |