Consolidated Statements Of Operations And Comprehensive Income/(Loss) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
INTEREST AND DIVIDEND INCOME
Loan receivable	$ 364,580	$ 380,662	$ 401,831
Investment securities-taxable	83,083	106,568	123,939
Investment securities-nontaxable	4,218	854	788
Federal Home Loan Bank stock	177	237	149
Federal funds sold and securities purchased under agreement to resell	83	14	1,351
Deposits with banks	1,430	1,259	673
Total interest and dividend income	453,571	489,594	528,731
INTEREST EXPENSE
Time deposits of $100,000 or more	42,204	54,219	83,349
Other deposits	20,010	29,943	50,207
Interest on securities sold under agreements to repurchase	60,733	66,141	65,182
Advances from the Federal Home Loan Bank	12,033	37,527	42,442
Long-term debt	4,890	3,852	4,835
Short-term borrowings	11	6	24
Total interest expense	139,881	191,688	246,039
Net interest income before provision for credit losses	313,690	297,906	282,692
Provision for credit losses	27,000	156,900	307,000
Net interest income/(loss) after provision for credit losses	286,690	141,006	(24,308)
NON-INTEREST INCOME
Securities gains, net	21,131	18,695	55,644
Letters of credit commissions	5,644	4,466	4,216
Depository service fees	5,420	5,220	5,206
Other operating income	18,697	3,870	13,588
Total non-interest income .	50,892	32,251	78,654
NON-INTEREST EXPENSE
Salaries and employee benefits	71,849	58,835	60,795
Occupancy expense	14,225	12,188	16,109
Computer and equipment expense	8,508	8,230	7,856
Professional services expense	20,209	17,630	16,428
FDIC and State assessments	12,494	19,549	19,386
Marketing expense	3,175	3,160	2,593
Other real estate owned	10,583	16,011	36,075
Operations of investments in affordable housing	8,153	7,611	7,338
Amortization of core deposit premium	5,859	5,958	6,636
Cost associated with debt redemption	20,231	14,261
Other operating expense	10,280	12,278	9,821
Total non-interest expense	185,566	175,711	183,037
Income/(loss) before income tax (benefit)/expense	152,016	(2,454)	(128,691)
Income tax expense/(benefit)	51,261	(14,629)	(61,912)
Net income/(loss)	100,755	12,175	(66,779)
Less: net income attributable to noncontrolling interest	605	610	611
Net income/(loss) attributable to Cathay General Bancorp	100,150	11,565	(67,390)
Dividends on preferred stock	(16,437)	(16,388)	(16,338)
Net income/(loss) attributable to common stockholders	83,713	(4,823)	(83,728)
Other comprehensive loss, net of tax:
Unrealized holding gains/(losses) arising during the year	4,538	7,714	(806)
Less: reclassification adjustment for gains included in net income	12,248	7,860	23,396
Total other comprehensive loss, net of tax	(7,710)	(146)	(24,202)
Total comprehensive income/(loss)	$ 92,440	$ 11,419	$ (91,592)
Net income/(loss) attributable to common stockholders per common share
Basic	$ 1.06	$ (0.06)	$ (1.59)
Diluted	$ 1.06	$ (0.06)	$ (1.59)
Basic average common shares outstanding	78,633,317	77,073,954	52,629,159
Diluted average common shares outstanding	78,640,652	77,073,954	52,629,159