INVESTMENT SECURITIES (Details 2) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013
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	$ 593,853,000	$ 773,925,000
Less Than 12 Months, Gross Unrealized Losses	(11,885,000)	(33,356,000)
12 months or Longer, Carrying Value	99,872,000	5,032,000
12 months or Longer, Gross Unrealized Losses	(7,363,000)	(189,000)
Total, Carrying Value	693,725,000	778,957,000
Total, Gross Unrealized Losses	(19,248,000)	(33,545,000)
Amortized Cost
Due in one year or less	3,585,000
Due after one year through five years	24,390,000
Due after five years through ten years	266,745,000
Due after ten years	1,170,985,000
Total securities available-for-sale	1,465,705,000	1,500,516,000
Carrying Value
Due in one year or less	3,587,000
Due after one year through five years	24,614,000
Due after five years through ten years	265,949,000
Due after ten years	1,183,323,000
Carrying Value	1,477,473,000	1,494,745,000
Interest income on investment securities
Taxable interest	6,920,000	6,564,000	5,563,000
Nontaxable interest	3,328,000	3,333,000	2,425,000
Dividend income	575,000	525,000	228,000
Total interest income on investment securities	10,823,000	10,422,000	8,216,000
FHLB Stock
Investment in Federal Home Loan Bank stock carried at cost	25,000,000	27,939,000
Decrease in FHLB stock	2,900,000
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	119,687,000	148,662,000
Less Than 12 Months, Gross Unrealized Losses	(1,381,000)	(2,767,000)
12 months or Longer, Carrying Value	673,000	32,000
12 months or Longer, Gross Unrealized Losses	(158,000)	(1,000)
Total, Carrying Value	120,360,000	148,694,000
Total, Gross Unrealized Losses	(1,539,000)	(2,768,000)
Amortized Cost
Total securities available-for-sale	560,004,000	691,944,000
Carrying Value
Carrying Value	574,669,000	707,188,000
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	218,387,000	179,938,000
Less Than 12 Months, Gross Unrealized Losses	(3,957,000)	(4,486,000)
12 months or Longer, Carrying Value		4,383,000
12 months or Longer, Gross Unrealized Losses		(98,000)
Total, Carrying Value	218,387,000	184,321,000
Total, Gross Unrealized Losses	(3,957,000)	(4,584,000)
Amortized Cost
Total securities available-for-sale	272,832,000	197,069,000
Carrying Value
Carrying Value	269,637,000	192,873,000
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	89,000	1,640,000
Less Than 12 Months, Gross Unrealized Losses	(1,000)	(60,000)
12 months or Longer, Carrying Value	1,047,000	617,000
12 months or Longer, Gross Unrealized Losses	(86,000)	(90,000)
Total, Carrying Value	1,136,000	2,257,000
Total, Gross Unrealized Losses	(87,000)	(150,000)
Amortized Cost
Total securities available-for-sale	29,649,000	30,502,000
Carrying Value
Carrying Value	37,594,000	37,904,000
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	175,910,000	337,208,000
Less Than 12 Months, Gross Unrealized Losses	(5,984,000)	(24,273,000)
12 months or Longer, Carrying Value	98,152,000
12 months or Longer, Gross Unrealized Losses	(7,119,000)
Total, Carrying Value	274,062,000	337,208,000
Total, Gross Unrealized Losses	(13,103,000)	(24,273,000)
Amortized Cost
Total securities available-for-sale	455,437,000	459,182,000
Carrying Value
Carrying Value	447,933,000	436,658,000
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	37,294,000	72,636,000
Less Than 12 Months, Gross Unrealized Losses	(307,000)	(1,483,000)
Total, Carrying Value	37,294,000	72,636,000
Total, Gross Unrealized Losses	(307,000)	(1,483,000)
Amortized Cost
Total securities available-for-sale	84,210,000	84,119,000
Carrying Value
Carrying Value	84,211,000	82,707,000
Government-sponsored enterprise 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	25,936,000	9,872,000
Less Than 12 Months, Gross Unrealized Losses	(200,000)	(174,000)
Total, Carrying Value	25,936,000	9,872,000
Total, Gross Unrealized Losses	(200,000)	(174,000)
Amortized Cost
Total securities available-for-sale	36,180,000	10,046,000
Carrying Value
Carrying Value	36,054,000	9,872,000
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	16,550,000	23,969,000
Less Than 12 Months, Gross Unrealized Losses	(55,000)	(113,000)
Total, Carrying Value	16,550,000	23,969,000
Total, Gross Unrealized Losses	(55,000)	(113,000)
Amortized Cost
Total securities available-for-sale	27,393,000	27,654,000
Carrying Value
Carrying Value	$ 27,375,000	$ 27,543,000