Loans Held for Sale - Narrative (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Receivables Held-for-sale [Abstract]
Loans held-for-sale (including nonperforming loans)	$ 18.9	$ 1.3

Loans Held-for-Sale (Including Nonperforming Loans)

No definition available.

Name:	cubi_LoansHeldForSaleIncludingNonperformingLoans
Namespace Prefix:	cubi_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant