REGULATORY REQUIREMENTS (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2009
Actual
Total Capital (to Risk-Weighted Assets), Amount	$ 2,296,253,000	$ 2,296,274,000
Tier I Capital (to Risk-Weighted Assets), Amount	2,116,757,000	2,074,963,000
Tier I Capital (to Average Assets), Amount	2,116,757,000	2,074,963,000
Total Capital (to Risk-Weighted Assets), Ratio (as a percent)	16.10%	16.40%
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent)	14.80%	14.80%
Tier I Capital (to Average Assets), Ratio (as a percent)	9.60%	9.70%
For Capital Adequacy Purposes
Total Capital (to Risk-Weighted Assets), Amount	1,142,743,000	1,123,413,000
Tier I Capital (to Risk-Weighted Assets), Amount	571,371,000	561,706,000
Tier I Capital (to Average Assets), Amount	880,526,000	859,098,000
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	6.30%	6.40%
East West Bank
Actual
Total Capital (to Risk-Weighted Assets), Amount	2,225,888,000	2,283,178,000
Tier I Capital (to Risk-Weighted Assets), Amount	2,046,477,000	2,061,896,000
Tier I Capital (to Average Assets), Amount	2,046,477,000	2,061,896,000
Total Capital (to Risk-Weighted Assets), Ratio (as a percent)	15.60%	16.30%
Tier I Capital (to Risk-Weighted Assets), Ratio (as a percent)	14.30%	14.70%
Tier I Capital (to Average Assets), Ratio (as a percent)	9.30%	9.60%
For Capital Adequacy Purposes
Total Capital (to Risk-Weighted Assets), Amount	1,142,215,000	1,123,228,000
Tier I Capital (to Risk-Weighted Assets), Amount	571,107,000	561,614,000
Tier I Capital (to Average Assets), Amount	880,162,000	858,765,000
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	1,427,769,000	1,404,035,000
Tier I Capital (to Risk-Weighted Assets), Amount	856,661,000	842,421,000
Tier I Capital (to Average Assets), Amount	1,100,202,000	1,073,457,000
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	$ 228,700,000	$ 186,500,000