Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Jun. 30, 2013	Feb. 14, 2013
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			79,589,933
Entity Public Float		$ 1,468,916,500
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	No
Document Period End Date	Dec. 31, 2013
Document Fiscal Year Focus	2013
Document Fiscal Period Focus	FY