REGULATORY REQUIREMENTS (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Actual
Total Capital (to Risk-Weighted Assets), Amount	$ 2,296,274,000	$ 2,075,480,000
Tier I Capital (to Risk-Weighted Assets), Amount	2,074,963,000	1,865,602,000
Tier I Capital (to Average Assets), Amount	2,074,963,000	1,865,602,000
Total Capital (to Risk-Weighted Assets), Ratio (as a percent)	16.40%	17.50%
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent)	14.80%	15.70%
Tier I Capital (to Average Assets), Ratio (as a percent)	9.70%	9.30%
For Capital Adequacy Purposes
Total Capital (to Risk-Weighted Assets), Amount	1,123,413,000	950,680,000
Tier I Capital (to Risk-Weighted Assets), Amount	561,706,000	475,340,000
Tier I Capital (to Average Assets), Amount	859,098,000	801,850,000
Total Capital (to Risk-Weighted Assets), Ratio (as a percent)	8.00%	8.00%
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent)	4.00%	4.00%
Tier I Capital (to Average Assets), Ratio (as a percent)	4.00%	4.00%
Regulatory Requirements - Additional Disclosure
Minimum total consolidated assets for exclusion of trust preferred securities as Tier I regulatory capital	15,000,000,000		15,000,000,000
Trust preferred securities as a percentage of the Company's Tier I capital	6.40%	8.30%
East West Bank
Actual
Total Capital (to Risk-Weighted Assets), Amount	2,283,178,000	2,068,922,000
Tier I Capital (to Risk-Weighted Assets), Amount	2,061,896,000	1,859,102,000
Tier I Capital (to Average Assets), Amount	2,061,896,000	1,859,102,000
Total Capital (to Risk-Weighted Assets), Ratio (as a percent)	16.30%	17.40%
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent)	14.70%	15.70%
Tier I Capital (to Average Assets), Ratio (as a percent)	9.60%	9.30%
For Capital Adequacy Purposes
Total Capital (to Risk-Weighted Assets), Amount	1,123,228,000	950,301,000
Tier I Capital (to Risk-Weighted Assets), Amount	561,614,000	475,151,000
Tier I Capital (to Average Assets), Amount	858,765,000	800,863,000
Total Capital (to Risk-Weighted Assets), Ratio (as a percent)	8.00%	8.00%
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent)	4.00%	4.00%
Tier I Capital (to Average Assets), Ratio (as a percent)	4.00%	4.00%
To Be Well Capitalized Under Prompt Corrective Action Provisions
Total Capital (to Risk-Weighted Assets), Amount	1,404,035,000	1,187,877,000
Tier I Capital (to Risk-Weighted Assets), Amount	842,421,000	712,726,000
Tier I Capital (to Average Assets), Amount	1,073,457,000	1,001,079,000
Total Capital (to Risk-Weighted Assets), Ratio (as a percent)	10.00%	10.00%
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent)	6.00%	6.00%
Tier I Capital (to Average Assets), Ratio (as a percent)	5.00%	5.00%
Reserve Requirement
Daily average reserve requirement	$ 186,500,000	$ 80,900,000