GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $)	12 Months Ended							12 Months Ended
	Dec. 31, 2011 Y Segment	Dec. 31, 2010	Mar. 31, 2010 Segment	Dec. 31, 2009	Nov. 30, 2009 Segment	Mar. 31, 2009 Segment	Dec. 31, 2008	Dec. 31, 2011 Premiums on acquired deposits	Dec. 31, 2010 Premiums on acquired deposits	Dec. 31, 2009 Premiums on acquired deposits	Dec. 31, 2010 Washington First International Bank Premiums on acquired deposits	Dec. 31, 2009 United Commercial Bank Premiums on acquired deposits
GOODWILL AND OTHER INTANGIBLE ASSETS
Goodwill	$ 337,438,000			$ 337,438,000
Market capitalization	2,990,000,000
Total stockholders' equity	2,311,743,000	2,113,931,000		2,284,659,000			1,550,766,000
Number of business divisions	3		3			3
Number of operating segments	3		3		4
Period for which the company provided a net income projection under the income approach to determine the fair value of the reporting units (in years)	5
Changes in carrying amount of goodwill
Balance, beginning of year	337,438,000			337,438,000
Balance, end of year	337,438,000			337,438,000
Premiums on Acquired Deposits
Premiums on acquired deposits								117,600,000	117,600,000		3,100,000	74,400,000
Accumulated amortization for premiums on acquired deposits								50,400,000	38,100,000
Amortization expense of premiums on acquired deposits								12,300,000	13,300,000	5,900,000
Estimated Future Amortization Expense of Premiums on Acquired Deposits
2012								10,906,000
2013								9,364,000
2014								8,454,000
2015								7,543,000
2016								6,634,000
Thereafter								24,289,000
Total								$ 67,190,000