Loans Receivable and Allowance for Credit Losses - Allowance for Credit Losses Narrative (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2022	Dec. 31, 2021
Loans and Leases Receivable Disclosure [Abstract]
Allowance for credit losses	$ 587.6	$ 569.1
Increase in allowance for credit losses	$ 18.5

Financing Receivable And Off Balance Sheet Credit Loss Allowance, Period Increase (Decrease)

No definition available.

Name:	ewbc_FinancingReceivableAndOffBalanceSheetCreditLossAllowancePeriodIncreaseDecrease
Namespace Prefix:	ewbc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration