Note 18 - Employee Benefit Plans	12 Months Ended
Dec. 31, 2015
Disclosure Text Block Supplement [Abstract]
Compensation and Employee Benefit Plans [Text Block]	18. Employee Benefit Plans Employee Stock Ownership Plan. Under the Company’s Amended and Restated Cathay Bank Employee Stock Ownership Plan (“ESOP”), the Company can make annual contributions to a trust in the form of either cash or common stock of the Bancorp for the benefit of eligible employees. Employees are eligible to participate in the ESOP after completing two years of service for salaried full-time employees or 1,000 hours for each of two consecutive years for salaried part-time employees. The amount of the annual contribution is discretionary except that it must be sufficient to enable the trust to meet its current obligations. The Company also pays for the administration of this plan and of the trust. The Company has not made contributions to the trust since 2004 and does not expect to make any contributions in the future. Effective June 17, 2004, the ESOP was amended to provide the participants the election either to reinvest the dividends on the Company stock allocated to their accounts or to have these dividends distributed to the participant. The ESOP trust purchased 18,012 shares in 2015, 11,887 shares in 2014, and 3,825 shares in 2013, of the Bancorp’s common stock at an aggregate cost of $541,000 in 2015, $301,902 in 2014, and $92,000 in 2013. The distribution of benefits to participants totaled 107,202 shares in 2015, 73,439 shares in 2014, and 51,779 shares in 2013. As of December 31, 2015, the ESOP owned 990,047 shares, or 1.2%, of the Company’s outstanding common stock. 401(k) Plan. In 1997, the Board approved the Company’s 401(k) Profit Sharing Plan, which began on March 1, 1997. Salaried employees who have completed three months of service and have attained the age of 21 are eligible to participate. Enrollment dates are on January 1st, April 1st, July 1st, and October 1st of each year. Participants may contribute up to 75% of their eligible compensation for the year but not to exceed the dollar limit set by the Internal Revenue Code. Participants may change their contribution election on the enrollment dates. The vesting schedule for the matching contribution is 0% for less than two years of service, 25% after two years of service and from then on, at an increment of 25% each year until 100% is vested after five years of service. Effective on October 1, 2014, the Company matches 100% on the first 4.0% of eligible compensation contributed per pay period by the participant, after one year of service. The Company’s contribution amounted to $2.0 million in 2015, $1.4 million in 2014, and $1.0 million in 2013. The Plan allows participants to withdraw all or part of their vested amount in the Plan due to certain financial hardship as set forth in the Internal Revenue Code and Treasury Regulations. Participants may also borrow up to 50% of the vested amount, with a maximum of $50,000. The minimum loan amount is $1,000.

Note 18 - Employee Benefit Plans

12 Months Ended

Dec. 31, 2015

Disclosure Text Block Supplement [Abstract]

Compensation and Employee Benefit Plans [Text Block]

18. Employee Benefit Plans

Employee Stock Ownership Plan. Under the Company’s Amended and Restated Cathay Bank Employee Stock Ownership Plan (“ESOP”), the Company can make annual contributions to a trust in the form of either cash or common stock of the Bancorp for the benefit of eligible employees. Employees are eligible to participate in the ESOP after completing two years of service for salaried full-time employees or 1,000 hours for each of two consecutive years for salaried part-time employees. The amount of the annual contribution is discretionary except that it must be sufficient to enable the trust to meet its current obligations. The Company also pays for the administration of this plan and of the trust. The Company has not made contributions to the trust since 2004 and does not expect to make any contributions in the future. Effective June 17, 2004, the ESOP was amended to provide the participants the election either to reinvest the dividends on the Company stock allocated to their accounts or to have these dividends distributed to the participant. The ESOP trust purchased 18,012 shares in 2015, 11,887 shares in 2014, and 3,825 shares in 2013, of the Bancorp’s common stock at an aggregate cost of $541,000 in 2015, $301,902 in 2014, and $92,000 in 2013. The distribution of benefits to participants totaled 107,202 shares in 2015, 73,439 shares in 2014, and 51,779 shares in 2013. As of December 31, 2015, the ESOP owned 990,047 shares, or 1.2%, of the Company’s outstanding common stock.

401(k) Plan. In 1997, the Board approved the Company’s 401(k) Profit Sharing Plan, which began on March 1, 1997. Salaried employees who have completed three months of service and have attained the age of 21 are eligible to participate. Enrollment dates are on January 1st, April 1st, July 1st, and October 1st of each year. Participants may contribute up to 75% of their eligible compensation for the year but not to exceed the dollar limit set by the Internal Revenue Code. Participants may change their contribution election on the enrollment dates. The vesting schedule for the matching contribution is 0% for less than two years of service, 25% after two years of service and from then on, at an increment of 25% each year until 100% is vested after five years of service. Effective on October 1, 2014, the Company matches 100% on the first 4.0% of eligible compensation contributed per pay period by the participant, after one year of service. The Company’s contribution amounted to $2.0 million in 2015, $1.4 million in 2014, and $1.0 million in 2013. The Plan allows participants to withdraw all or part of their vested amount in the Plan due to certain financial hardship as set forth in the Internal Revenue Code and Treasury Regulations. Participants may also borrow up to 50% of the vested amount, with a maximum of $50,000. The minimum loan amount is $1,000.