Summary of Significant Accounting Policies (Details) $ in Millions	3 Months Ended
Mar. 31, 2022 USD ($)
Accounting Policies [Abstract]
Fair value of debt securities from AFS to HTM	$ 3,010

Debt Securities, Available-for-sale, Transfer to Held to Maturity, Amount

No definition available.

Name:	ewbc_DebtSecuritiesAvailableForSaleTransferToHeldToMaturityAmount
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration