INVESTMENT SECURITIES (Details 2) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 29, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Carrying values and gross unrealized losses on securities by length of time the securities were in an unrealized loss position
Less Than 12 Months, Carrying Value	$ 192,738,000				$ 71,658,000				$ 192,738,000	$ 71,658,000
Less Than 12 Months, Gross Unrealized Losses	(2,616,000)				(897,000)				(2,616,000)	(897,000)
12 months or Longer, Carrying Value	1,752,000				5,979,000				1,752,000	5,979,000
12 months or Longer, Gross Unrealized Losses	(124,000)				(1,576,000)				(124,000)	(1,576,000)
Total, Carrying Value	194,490,000				77,637,000				194,490,000	77,637,000
Total, Gross Unrealized Losses	(2,740,000)				(2,473,000)				(2,740,000)	(2,473,000)
OTTI charges			1,115,000						1,115,000		874,000
FDIC loss sharing income	(6,022,000)	(367,000)	(102,000)	(3,579,000)	2,667,000	963,000	5,316,000	(1,170,000)	(10,070,000)	7,776,000	22,784,000
Amortized Cost
Due in one year or less	11,687,000								11,687,000
Due after one year through five years	3,180,000								3,180,000
Due after five years through ten years	31,013,000								31,013,000
Due after ten years	1,252,781,000								1,252,781,000
Total securities available-for-sale	1,298,661,000				1,287,042,000				1,298,661,000	1,287,042,000
Carrying Value
Due in one year or less	16,185,000								16,185,000
Due after one year through five years	3,311,000								3,311,000
Due after five years through ten years	33,008,000								33,008,000
Due after ten years	1,302,881,000								1,302,881,000
Carrying Value	1,355,385,000				1,326,358,000				1,355,385,000	1,326,358,000
FHLB Stock
Investment in Federal Home Loan Bank stock carried at cost	37,126,000				46,106,000				37,126,000	46,106,000
Government agency and government-sponsored enterprise pass through securities
Carrying values and gross unrealized losses on securities by length of time the securities were in an unrealized loss position
Less Than 12 Months, Carrying Value	67,299,000				34,682,000				67,299,000	34,682,000
Less Than 12 Months, Gross Unrealized Losses	(452,000)				(64,000)				(452,000)	(64,000)
12 months or Longer, Carrying Value	60,000				22,000				60,000	22,000
12 months or Longer, Gross Unrealized Losses	(1,000)				(1,000)				(1,000)	(1,000)
Total, Carrying Value	67,359,000				34,704,000				67,359,000	34,704,000
Total, Gross Unrealized Losses	(453,000)				(65,000)				(453,000)	(65,000)
Amortized Cost
Total securities available-for-sale	774,677,000				1,011,222,000				774,677,000	1,011,222,000
Carrying Value
Carrying Value	807,842,000				1,042,507,000				807,842,000	1,042,507,000
Government agency and government-sponsored enterprise collateralized mortgage obligations
Carrying values and gross unrealized losses on securities by length of time the securities were in an unrealized loss position
Less Than 12 Months, Carrying Value	18,317,000				10,790,000				18,317,000	10,790,000
Less Than 12 Months, Gross Unrealized Losses	(132,000)				(21,000)				(132,000)	(21,000)
12 months or Longer, Carrying Value					1,530,000					1,530,000
12 months or Longer, Gross Unrealized Losses					(15,000)					(15,000)
Total, Carrying Value	18,317,000				12,320,000				18,317,000	12,320,000
Total, Gross Unrealized Losses	(132,000)				(36,000)				(132,000)	(36,000)
Amortized Cost
Total securities available-for-sale	99,956,000				80,353,000				99,956,000	80,353,000
Carrying Value
Carrying Value	101,694,000				82,027,000				101,694,000	82,027,000
Covered private label collateralized mortgage obligations
Carrying values and gross unrealized losses on securities by length of time the securities were in an unrealized loss position
Less Than 12 Months, Carrying Value					5,228,000					5,228,000
Less Than 12 Months, Gross Unrealized Losses					(595,000)					(595,000)
12 months or Longer, Carrying Value	1,692,000				4,427,000				1,692,000	4,427,000
12 months or Longer, Gross Unrealized Losses	(123,000)				(1,560,000)				(123,000)	(1,560,000)
Total, Carrying Value	1,692,000				9,655,000				1,692,000	9,655,000
Total, Gross Unrealized Losses	(123,000)				(2,155,000)				(123,000)	(2,155,000)
Number of securities impaired due to deteriorating cash flows	2								2		2
OTTI charges									1,100,000		874,000
FDIC loss sharing income									892,000		699,000
Amortized Cost
Total securities available-for-sale	36,078,000				41,426,000				36,078,000	41,426,000
Carrying Value
Carrying Value	44,684,000				45,149,000				44,684,000	45,149,000
Municipal securities
Carrying values and gross unrealized losses on securities by length of time the securities were in an unrealized loss position
Less Than 12 Months, Carrying Value	90,303,000				7,755,000				90,303,000	7,755,000
Less Than 12 Months, Gross Unrealized Losses	(1,951,000)				(56,000)				(1,951,000)	(56,000)
Total, Carrying Value	90,303,000				7,755,000				90,303,000	7,755,000
Total, Gross Unrealized Losses	(1,951,000)				(56,000)				(1,951,000)	(56,000)
Amortized Cost
Total securities available-for-sale	339,547,000				124,079,000				339,547,000	124,079,000
Carrying Value
Carrying Value	348,041,000				126,797,000				348,041,000	126,797,000
Corporate debt securities
Carrying values and gross unrealized losses on securities by length of time the securities were in an unrealized loss position
Less Than 12 Months, Carrying Value	16,819,000				10,758,000				16,819,000	10,758,000
Less Than 12 Months, Gross Unrealized Losses	(81,000)				(26,000)				(81,000)	(26,000)
Total, Carrying Value	16,819,000				10,758,000				16,819,000	10,758,000
Total, Gross Unrealized Losses	(81,000)				(26,000)				(81,000)	(26,000)
Amortized Cost
Total securities available-for-sale	42,014,000				25,077,000				42,014,000	25,077,000
Carrying Value
Carrying Value	42,365,000				25,128,000				42,365,000	25,128,000
Other securities
Carrying values and gross unrealized losses on securities by length of time the securities were in an unrealized loss position
Less Than 12 Months, Carrying Value					2,445,000					2,445,000
Less Than 12 Months, Gross Unrealized Losses					(135,000)					(135,000)
Total, Carrying Value					2,445,000					2,445,000
Total, Gross Unrealized Losses					(135,000)					(135,000)
Amortized Cost
Total securities available-for-sale	6,389,000				4,885,000				6,389,000	4,885,000
Carrying Value
Carrying Value	$ 10,759,000				$ 4,750,000				$ 10,759,000	$ 4,750,000