PARENT COMPANY FINANCIAL STATEMENTS (Details 3) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 71,900	$ 71,110	$ 70,557	$ 68,083	$ 66,206	$ 62,432	$ 60,525	$ 56,071	$ 281,650	$ 245,234	$ 164,564
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									82,536	67,460	57,593
Stock compensation costs									13,238	13,543	8,761
Gain on sales of investment securities available-for-sale									(757)	(9,700)	(31,200)
Net cash provided by operating activities									287,526	255,317	869,196
Purchases of:
Investment securities available-for-sale									(1,835,823)	(2,713,546)	(4,207,000)
Proceeds from:
Repayments, maturities and redemptions of investment									1,119,098	1,780,457	2,564,157
Sale/call of investment securities available-for-sale									1,230,134	702,616	1,338,910
Net cash (used in) provided by investing activities									(758,905)	(1,071,226)	93,233
Payment for:
Repayment of long-term debt									(75,000)	(23,918)
Repurchase of Series B preferred stock											(306,546)
Repurchase of common stock warrants										(14,500)
Repurchase of shares of treasury stock pursuant to the Stock Repurchase Plan									(199,950)
Proceeds from:
Issuance of common stock pursuant to various stock plans and agreements									3,821	5,726	4,454
Net cash provided by (used in) financing activities									364,200	914,211	(729,671)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS									(108,079)	97,236	234,865
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				1,431,185				1,333,949	1,431,185	1,333,949	1,099,084
CASH AND CASH EQUIVALENTS, END OF YEAR	1,323,106				1,431,185				1,323,106	1,431,185	1,333,949
Cash paid during the year for:
Interest									136,760	175,772	206,706
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									281,650	245,234	164,564
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed (income) of subsidiaries									(285,636)	(250,513)	(169,515)
Depreciation and amortization									445	1,034	623
Prepayment penalty on other borrowings										526
Stock compensation costs										1,767	8,761
Gain on sales of investment securities available-for-sale											(556)
Tax provision (benefit) from stock plans									(462)	(717)	170
Net change in other assets									322,361	73,797	83,395
Net change in other liabilities									(259)	(3,709)	(596)
Net cash provided by operating activities									318,099	67,419	86,846
Purchases of:
Investment securities available-for-sale											(20,746)
Proceeds from:
Redemption of certificates of deposit										198	17,516
Sale/call of investment securities available-for-sale											48,224
Net cash (used in) provided by investing activities										198	44,994
Payment for:
Repayment of long-term debt										(23,918)
Purchase of treasury shares									(3,012)	(649)	(1,207)
Cash dividends on preferred stock									(6,857)	(6,857)	(24,060)
Cash dividends on common stock									(57,361)	(23,822)	(5,545)
Repurchase of Series B preferred stock											(306,546)
Repurchase of common stock warrants										(14,500)
Repurchase of shares of treasury stock pursuant to the Stock Repurchase Plan									(199,950)
Proceeds from:
Issuance of common stock pursuant to various stock plans and agreements									3,821	5,726	4,454
Tax (benefit) provision from stock plans									462	717	(170)
Net cash provided by (used in) financing activities									(262,897)	(63,303)	(333,074)
NET (DECREASE) INCREASE IN CASH AND CASH EQUIVALENTS									55,202	4,314	(201,234)
CASH AND CASH EQUIVALENTS, BEGINNING OF YEAR				9,287				4,973	9,287	4,973	206,207
CASH AND CASH EQUIVALENTS, END OF YEAR	64,489				9,287				64,489	9,287	4,973
Cash paid during the year for:
Interest									3,112	5,167	5,306
Noncash investing and financing activities:
Conversion of preferred stock to common stock										31	325,299
Amortization of preferred stock discount											21,042
Issuance of common stock in lieu of Board of Director retainer fees									$ 570	$ 520	$ 281