Business Combinations (Details) (USD $)	12 Months Ended			1 Months Ended	12 Months Ended				12 Months Ended	1 Months Ended		1 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Apr. 30, 2011 Nevada Commerce Bank	Dec. 31, 2011 Nevada Commerce Bank Y	Apr. 08, 2011 Nevada Commerce Bank	Feb. 11, 2011 Branch office in San Jose	Nov. 15, 2010 Datafaction Inc	Dec. 31, 2011 Sun West Bank and 1st Pacific Bank of California Y	May 31, 2010 Sun West Bank	May 28, 2010 Sun West Bank	May 31, 2010 1st Pacific Bank of California	May 07, 2010 1st Pacific Bank of California
Business acquisitions
Deposits	$ (126,795,000)	$ (541,499,000)	$ (2,113,195,000)			$ 118,400,000	$ 8,400,000				$ 304,300,000		$ 237,200,000
Acquired goodwill							300,000	6,200,000
Core deposit intangible						900,000	100,000
Customer contract intangible								2,200,000
Carrying value of assets acquired						138,900,000					340,000,000		318,600,000
Carrying value of liabilities assumed						121,900,000					310,100,000		264,200,000
Covered loans	55,313,000	330,566,000	1,862,515,000			56,400,000					127,600,000		202,800,000
Covered other real estate owned	7,463,000	15,161,000	58,761,000			7,500,000					12,100,000
Cash paid on acquisition													12,300,000
Cash from the FDIC						2,700,000					29,200,000
FDIC reimbursement (as a percent)					80.00%				80.00%
Term of loss-sharing agreements for single family residential loans (in years)					10				10
Term of loss-sharing agreements for other loans (in years)					8				8
FDIC indemnification asset	204,259,000	295,466,000				33,800,000					104,600,000		36,500,000
FDIC liability													3,600,000
Gain on acquisition	8,164,000	27,339,000	38,206,000	8,200,000						24,700,000		2,600,000
Acquisition related expense				$ 300,000