Capital Resources (Outstanding Junior Subordinated Notes Issued) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011
Subordinated Borrowing [Line Items]
Junior Subordinated Notes	$ 121,136
Cathay Capital Trust I [Member]
Subordinated Borrowing [Line Items]
Issuance Date	June 26, 2003
Junior Subordinated Notes	20,619
Not Redeemable Until	June 30, 2008
Stated Maturity	Jun. 30, 2033
Annualized Coupon Rate	3-month LIBOR +3.15%
Current Interest Rate	3.73%
Date of Rate Change	December 30, 2011
Payable/Distribution Date	March 30 June 30 September 30 December 30
Cathay Statutory Trust I [Member]
Subordinated Borrowing [Line Items]
Issuance Date	September 17, 2003
Junior Subordinated Notes	20,619
Not Redeemable Until	September 17, 2008
Stated Maturity	Sep. 17, 2033
Annualized Coupon Rate	3-month LIBOR+3.00%
Current Interest Rate	3.56%
Date of Rate Change	December 17, 2011
Payable/Distribution Date	March 17 June 17 September 17 December 17
Cathay Capital Trust II [Member]
Subordinated Borrowing [Line Items]
Issuance Date	December 30, 2003
Junior Subordinated Notes	12,887
Not Redeemable Until	March 30, 2009
Stated Maturity	Mar. 30, 2034
Annualized Coupon Rate	3-month LIBOR+2.90%
Current Interest Rate	3.48%
Date of Rate Change	December 30, 2011
Payable/Distribution Date	March 30 June 30 September 30 December 30
Cathay Capital Trust III [Member]
Subordinated Borrowing [Line Items]
Issuance Date	March 28, 2007
Junior Subordinated Notes	46,392
Not Redeemable Until	June 15, 2012
Stated Maturity	Jun. 15, 2037
Annualized Coupon Rate	3-month LIBOR+1.48%
Current Interest Rate	2.03%
Date of Rate Change	December 15, 2011
Payable/Distribution Date	March 15 June 15 September 15 December 15
Cathay Capital Trust IV [Member]
Subordinated Borrowing [Line Items]
Issuance Date	May 31, 2007
Junior Subordinated Notes	$ 20,619
Not Redeemable Until	September 6, 2012
Stated Maturity	Sep. 06, 2037
Annualized Coupon Rate	3-month LIBOR 1.40%
Current Interest Rate	1.93%
Date of Rate Change	December 6, 2011
Payable/Distribution Date	March 6 June 6 September 6 December 6