Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 17, 2015	Jun. 30, 2014
Document and Entity Information [Abstract]
Entity Registrant Name	CATHAY GENERAL BANCORP
Document Type	10-K
Current Fiscal Year End Date	--12-31
Entity Common Stock, Shares Outstanding		79,821,331
Entity Public Float			$ 1,862,531,231
Amendment Flag	false
Entity Central Index Key	0000861842
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Well-known Seasoned Issuer	Yes
Document Period End Date	Dec. 31, 2014
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY