PARENT COMPANY FINANCIAL STATEMENTS (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 66,206	$ 62,432	$ 60,525	$ 56,071	$ 56,349	$ 46,951	$ 36,348	$ 24,916	$ 245,234	$ 164,564	$ 76,642
Adjustments to reconcile net income after extraordinary items to net cash provided by operating activities:
Depreciation and amortization									67,460	57,593	81,901
Stock compensation costs									13,543	8,761	5,549
Net cash provided by operating activities									255,317	869,196	155,275
Purchases of:
Investment securities available-for-sale									(2,713,546)	(4,207,000)	(1,976,701)
Proceeds from sale of:
Sale/call of investment securities available-for-sale									702,616	1,338,910	1,650,680
Net cash (used in) provided by investing activities									(1,071,226)	93,233	1,448,034
Payment for:
Repayment of long-term debt									(23,918)
Repurchase of Series B preferred stock										(306,546)
Repurchase of common stock warrants									(14,500)
Proceeds from:
Issuance of common stock pursuant to various stock plans and agreements									5,726	4,454	949
Issuance of preferred stock, net of stock issuance costs, and common stock warrants											335,047
Net cash provided by (used in) financing activities									914,211	(729,671)	(1,383,078)
NET INCREASE IN CASH AND CASH EQUIVALENTS									97,236	234,865	220,231
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				1,333,949				1,099,084	1,333,949	1,099,084	878,853
CASH AND CASH EQUIVALENTS, END OF YEAR	1,431,185				1,333,949				1,431,185	1,333,949	1,099,084
Cash paid during the year for:
Interest									175,772	206,706	230,667
Noncash investing and financing activities:
Conversion of preferred stock to common stock									31	325,299
East West Bancorp, Inc.
CASH FLOWS FROM OPERATING ACTIVITIES
Net income									245,234	164,564	76,642
Adjustments to reconcile net income after extraordinary items to net cash provided by operating activities:
Equity in undistributed income (loss) of subsidiaries									(178,513)	(84,515)	(62,019)
Depreciation and amortization									1,034	623	470
Impairment write-down on investment securities available-for-sale,											5,863
Impairment writedown on other investments,											581
Prepayment penalty on other borrowings									526
Stock compensation costs									1,767	8,761	5,330
Gain on sales of investment securities available-for-sale										(556)
Tax provision (benefit) from stock plans									(717)	170	(1,012)
Net change in other assets									1,797	(1,605)	(1,841)
Net change in other liabilities									(3,709)	(596)	4,509
Net cash provided by operating activities									67,419	86,846	28,523
Purchases of:
Investment securities available-for-sale										(20,746)	(31,981)
Certificates of deposit											(17,714)
Proceeds from sale of:
Redemption of certificates of deposit									198	17,516
Sale/call of investment securities available-for-sale										48,224	5,000
Capital contributions to subsidiaries, net											(350,000)
Net cash (used in) provided by investing activities									198	44,994	(394,695)
Payment for:
Repayment of long-term debt									(23,918)
Purchase of treasury shares									(649)	(1,207)	(430)
Cash dividends on preferred stock									(6,857)	(24,060)	(26,076)
Cash dividends on common stock									(23,822)	(5,545)	(3,586)
Repurchase of Series B preferred stock										(306,546)
Repurchase of common stock warrants									(14,500)
Proceeds from:
Issuance of common stock pursuant to various stock plans and agreements									5,726	4,454	263,336
Issuance of preferred stock, net of stock issuance costs, and common stock warrants											325,120
Tax (provision) benefit from stock plans									(717)	170
Net cash provided by (used in) financing activities									(63,303)	(333,074)	558,364
NET INCREASE IN CASH AND CASH EQUIVALENTS									4,314	(201,234)	192,192
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				4,973				206,207	4,973	206,207	14,015
CASH AND CASH EQUIVALENTS, END OF YEAR	9,287				4,973				9,287	4,973	206,207
Cash paid during the year for:
Interest									5,167	5,306	6,373
Noncash investing and financing activities:
Conversion of preferred stock to common stock									31	325,299
Amortization of preferred stock discount										21,042	3,847
Issuance of common stock in lieu of Board of Director retainer fees									$ 520	$ 281	$ 219