Document And Entity Information - shares	6 Months Ended
	Jun. 30, 2016	Jul. 29, 2016
Document Information [Line Items]
Entity Registrant Name	Cathay General Bancorp
Entity Central Index Key	0000861842
Trading Symbol	caty
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	Yes
Entity Common Stock, Shares Outstanding (in shares)		78,862,106
Document Type	10-Q
Document Period End Date	Jun. 30, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q2
Amendment Flag	false