Derivatives - Schedule of the Net (Losses) Gains Recognized on the Company’s Consolidated Statement of Income Related to Derivatives Not Designated as Hedging Instruments (Details) - Derivatives not Designated as Hedging Instruments - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	$ 5,581	$ 12,302	$ 21,602	$ 24,249
Income Statement Location [Axis]: ewbc:CustomerDerivativeIncomeLossNetOfMarkToMarketAdjustments
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	(732)	(1,444)	202	(2,914)
Interest rate contracts | Income Statement Location [Axis]: ewbc:CustomerDerivativeIncomeLossNetOfMarkToMarketAdjustments
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	(1,272)	(1,907)	(25)	(3,309)
Credit contracts | Income Statement Location [Axis]: ewbc:CustomerDerivativeIncomeLossNetOfMarkToMarketAdjustments
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	(11)	(13)	(98)	(3)
Commodity contracts | Income Statement Location [Axis]: ewbc:CustomerDerivativeIncomeLossNetOfMarkToMarketAdjustments
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	551	476	325	398
Foreign exchange contracts | Income Statement Location [Axis]: ewbc:ForeignExchangeIncome
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	9,101	13,787	23,439	27,025
Equity contracts | Income Statement Location [Axis]: us-gaap:NoninterestIncomeOther
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	(2,729)	0	(2,041)	0
Equity contracts | Income Statement Location [Axis]: ewbc:LendingAndLoanServicingFees
Derivative Instruments, Gain (Loss) [Line Items]
Net derivative gains	$ (59)	$ (41)	$ 2	$ 138