PARENT COMPANY FINANCIAL STATEMENTS (Details) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
ASSETS
Cash and cash equivalents	$ 1,431,185	$ 1,333,949	$ 1,099,084	$ 878,853
Investment securities available-for-sale	3,072,578	2,875,941
Other assets	500,640	288,182
TOTAL	21,968,667	20,700,537	20,559,212
LIABILITIES AND STOCKHOLDERS' EQUITY
Long-term debt	212,178	235,570
Total liabilities	19,656,924	18,586,606
STOCKHOLDERS' EQUITY
Preferred stock, $0.001 par value, 5,000,000 shares authorized; Series A, non-cumulative convertible, 200,000 shares issued and 85,710 and 85,741 shares outstanding in 2011 and 2010, respectively.	83,027	83,058
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, $0.001 par value, 200,000,000 shares authorized; 156,798,011 and 155,743,241 shares issued in 2011 and 2010, respectively; 149,327,907 and 148,542,940 shares outstanding in 2011 and 2010, respectively.	157	156
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	156,798,011	155,743,241
Common stock, shares outstanding	149,327,907	148,542,940
Additional paid in capital	1,443,883	1,434,277
Retained earnings	934,617	720,116
Treasury stock, at cost - 7,470,104 shares in 2011 and 7,200,301 shares in 2010.	(116,001)	(111,262)
Treasury stock, shares	7,470,104	7,200,301
Accumulated other comprehensive (loss) income, net of tax	(33,940)	(12,414)
Total stockholders' equity	2,311,743	2,113,931	2,284,659	1,550,766
TOTAL	21,968,667	20,700,537
Preferred stock, Series A, non-cumulative convertible
STOCKHOLDERS' EQUITY
Preferred stock, $0.001 par value, 5,000,000 shares authorized; Series A, non-cumulative convertible, 200,000 shares issued and 85,710 and 85,741 shares outstanding in 2011 and 2010, respectively.	83,027	83,058
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	200,000	200,000
Preferred stock, shares outstanding	85,710	85,741
East West Bancorp, Inc.
ASSETS
Cash and cash equivalents	9,287	4,973	206,207	14,015
Certificates of deposit		198
Investment in subsidiaries	2,436,574	2,268,453
Other investments	538	1,136
Other assets	3,012	5,081
TOTAL	2,449,411	2,279,841
LIABILITIES AND STOCKHOLDERS' EQUITY
Long-term debt	137,178	160,570
Other liabilities	490	5,340
Total liabilities	137,668	165,910
STOCKHOLDERS' EQUITY
Common stock, $0.001 par value, 200,000,000 shares authorized; 156,798,011 and 155,743,241 shares issued in 2011 and 2010, respectively; 149,327,907 and 148,542,940 shares outstanding in 2011 and 2010, respectively.	157	156
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	156,798,011	155,743,241
Common stock, shares outstanding	149,327,907	148,542,940
Additional paid in capital	1,443,883	1,434,277
Retained earnings	934,617	720,116
Treasury stock, at cost - 7,470,104 shares in 2011 and 7,200,301 shares in 2010.	(116,001)	(111,262)
Treasury stock, shares	7,470,104	7,200,301
Accumulated other comprehensive (loss) income, net of tax	(33,940)	(12,414)
Total stockholders' equity	2,311,743	2,113,931
TOTAL	2,449,411	2,279,841
East West Bancorp, Inc. | Preferred stock, Series A, non-cumulative convertible
STOCKHOLDERS' EQUITY
Preferred stock, $0.001 par value, 5,000,000 shares authorized; Series A, non-cumulative convertible, 200,000 shares issued and 85,710 and 85,741 shares outstanding in 2011 and 2010, respectively.	$ 83,027	$ 83,058
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	200,000	200,000
Preferred stock, shares outstanding	85,710	85,741