Note 1 - Business	3 Months Ended
Mar. 31, 2013
Nature of Operations [Text Block]	1. Business Cathay General Bancorp (“Bancorp”) is the holding company for Cathay Bank (the “Bank” and, together, the “Company”), six limited partnerships investing in affordable housing investments in which the Bank is the sole limited partner, and GBC Venture Capital, Inc. The Bancorp also owns 100% of the common stock of five statutory business trusts created for the purpose of issuing capital securities. The Bank was founded in 1962 and offers a wide range of financial services. As of March 31, 2013, the Bank operated twenty branches in Southern California, eleven branches in Northern California, eight branches in New York State, three branches in Illinois, three branches in Washington State, two branches in Texas, one branch in Massachusetts, one branch in New Jersey, one branch in Hong Kong, and a representative office in Shanghai and in Taipei. Deposit accounts at the Hong Kong branch are not insured by the Federal Deposit Insurance Corporation (the “FDIC”).

Note 1 - Business

3 Months Ended

Mar. 31, 2013

1. Business

Cathay General Bancorp (“Bancorp”) is the holding company for Cathay Bank (the “Bank” and, together, the “Company”), six limited partnerships investing in affordable housing investments in which the Bank is the sole limited partner, and GBC Venture Capital, Inc. The Bancorp also owns 100% of the common stock of five statutory business trusts created for the purpose of issuing capital securities. The Bank was founded in 1962 and offers a wide range of financial services. As of March 31, 2013, the Bank operated twenty branches in Southern California, eleven branches in Northern California, eight branches in New York State, three branches in Illinois, three branches in Washington State, two branches in Texas, one branch in Massachusetts, one branch in New Jersey, one branch in Hong Kong, and a representative office in Shanghai and in Taipei. Deposit accounts at the Hong Kong branch are not insured by the Federal Deposit Insurance Corporation (the “FDIC”).