INVESTMENT SECURITIES (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Amortized Cost	$ 1,298,661,000	$ 1,287,042,000
Gross Unrealized Gains	59,464,000	41,789,000
Gross Unrealized Losses	(2,740,000)	(2,473,000)
Carrying Value	1,355,385,000	1,326,358,000
Market purchases of investment securities available-for-sale by utilizing excess liquidity	485,860,000	658,310,000	627,884,000
Proceeds from investment securities previously held in portfolio and/or obtained in acquisition	90,745,000
American Perspective
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Investment securities obtained in acquisition	48,900,000
Proceeds from investment securities previously held in portfolio and/or obtained in acquisition	45,600,000
Los Padres Bank
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Investment securities obtained in acquisition			33,600,000
Government agency and government-sponsored enterprise pass through securities
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Amortized Cost	774,677,000	1,011,222,000
Gross Unrealized Gains	33,618,000	31,350,000
Gross Unrealized Losses	(453,000)	(65,000)
Carrying Value	807,842,000	1,042,507,000
Proceeds from investment securities previously held in portfolio and/or obtained in acquisition	43,900,000
Gross realized gain	1,200,000
Government agency and government-sponsored enterprise collateralized mortgage obligations
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Amortized Cost	99,956,000	80,353,000
Gross Unrealized Gains	1,870,000	1,710,000
Gross Unrealized Losses	(132,000)	(36,000)
Carrying Value	101,694,000	82,027,000
Covered private label collateralized mortgage obligations
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Amortized Cost	36,078,000	41,426,000
Gross Unrealized Gains	8,729,000	5,878,000
Gross Unrealized Losses	(123,000)	(2,155,000)
Carrying Value	44,684,000	45,149,000
Municipal securities
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Amortized Cost	339,547,000	124,079,000
Gross Unrealized Gains	10,445,000	2,774,000
Gross Unrealized Losses	(1,951,000)	(56,000)
Carrying Value	348,041,000	126,797,000
Corporate debt securities
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Amortized Cost	42,014,000	25,077,000
Gross Unrealized Gains	432,000	77,000
Gross Unrealized Losses	(81,000)	(26,000)
Carrying Value	42,365,000	25,128,000
Other securities
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Amortized Cost	6,389,000	4,885,000
Gross Unrealized Gains	4,370,000
Gross Unrealized Losses		(135,000)
Carrying Value	10,759,000	4,750,000
Residential mortgage-backed securities issued by the Federal National Mortgage Association and federal Home Loan Mortgage Corporation
Amortized cost, gross unrealized gains and losses and estimated fair values of securities available-for-sale
Carrying Value	$ 829,800,000