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Bank Premises and Equipment - Narrative (Detail) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Property, Plant and Equipment [Abstract] |  |  |
Depreciation, occupancy and amortization of leasehold improvement | $ 2.5 | $ 3.4 | $ 2.7

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- Definition Depreciation, Occupancy and Amortization of Leasehold Improvement + References No definition available. + Details
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Namespace Prefix: | cubi_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- References No definition available. + Details
Name: | us-gaap_PropertyPlantAndEquipmentAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration