Regulatory Requirements and Matters (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Actual
Total Capital (to risk-weighted assets), Amount	$ 3,838,516	$ 3,400,642
Tier I Capital (to risk-weighted assets), Amount	3,390,070	2,976,002
Tier 1 Common Equity Capital (to risk-weighted assets), Amount	3,390,070	2,976,002
Tier 1 leverage capital (to adjusted average assets), Amount	3,390,070	2,976,002
Risk-weighted assets	29,669,251	27,357,753
Adjusted quarterly average total assets	$ 37,307,975	$ 34,209,827
Total Capital (to risk-weighted assets), Ratio (as a percent)	12.90%	12.40%
Tier I Capital (to risk-weighted assets), Ratio (as a percent)	11.40%	10.90%
Tier 1 Common Equity Capital (to risk-weighted assets), Ratio (as a percent)	11.40%	10.90%
Tier 1 leverage capital (to adjusted average assets), Ratio (as a percent)	9.20%	8.70%
Minimum Requirement
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)	6.00%	6.00%
Tier 1 Common Equity Capital (to risk-weighted assets), Ratio (as a percent)	4.50%	4.50%
Tier 1 leverage capital (to adjusted average assets), Ratio (as a percent)	4.00%	4.00%
Well Capitalized Requirement
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)	8.00%	8.00%
Tier 1 Common Equity Capital (to risk-weighted assets), Ratio (as a percent)	6.50%	6.50%
Tier 1 leverage capital (to adjusted average assets), Ratio (as a percent)	5.00%	5.00%
East West Bank
Actual
Total Capital (to risk-weighted assets), Amount	$ 3,679,261	$ 3,371,885
Tier I Capital (to risk-weighted assets), Amount	3,378,815	3,095,245
Tier 1 Common Equity Capital (to risk-weighted assets), Amount	3,378,815	3,095,245
Tier 1 leverage capital (to adjusted average assets), Amount	3,378,815	3,095,245
Risk-weighted assets	29,643,711	27,310,540
Adjusted quarterly average total assets	$ 37,283,273	$ 34,163,667
Total Capital (to risk-weighted assets), Ratio (as a percent)	12.40%	12.30%
Tier I Capital (to risk-weighted assets), Ratio (as a percent)	11.40%	11.30%
Tier 1 Common Equity Capital (to risk-weighted assets), Ratio (as a percent)	11.40%	11.30%
Tier 1 leverage capital (to adjusted average assets), Ratio (as a percent)	9.20%	9.10%
Minimum Requirement
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)	6.00%	6.00%
Tier 1 Common Equity Capital (to risk-weighted assets), Ratio (as a percent)	4.50%	4.50%
Tier 1 leverage capital (to adjusted average assets), Ratio (as a percent)	4.00%	4.00%
Well Capitalized Requirement
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)	8.00%	8.00%
Tier 1 Common Equity Capital (to risk-weighted assets), Ratio (as a percent)	6.50%	6.50%
Tier 1 leverage capital (to adjusted average assets), Ratio (as a percent)	5.00%	5.00%
Reserve Requirement
Daily average reserve requirement	$ 699,400	$ 503,800