INVESTMENT SECURITIES (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
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	$ 773,925				$ 192,738				$ 773,925	$ 192,738
Less Than 12 Months, Gross Unrealized Losses	(33,356)				(2,616)				(33,356)	(2,616)
12 months or Longer, Carrying Value	5,032				1,752				5,032	1,752
12 months or Longer, Gross Unrealized Losses	(189)				(124)				(189)	(124)
Total, Carrying Value	778,957				194,490				778,957	194,490
Total, Gross Unrealized Losses	(33,545)				(2,740)				(33,545)	(2,740)
OTTI charges							1,115			1,115
FDIC loss sharing income	(10,593)	(7,032)	(5,410)	(3,137)	(6,022)	(367)	(102)	(3,579)	(26,172)	(10,070)	7,776
Amortized Cost
Due in one year or less	5,775								5,775
Due after one year through five years	24,597								24,597
Due after five years through ten years	131,259								131,259
Due after ten years	1,338,885								1,338,885
Total securities available-for-sale	1,500,516				1,298,661				1,500,516	1,298,661
Carrying Value
Due in one year or less	5,792								5,792
Due after one year through five years	24,749								24,749
Due after five years through ten years	129,985								129,985
Due after ten years	1,334,219								1,334,219
Carrying Value	1,494,745				1,355,385				1,494,745	1,355,385
FHLB Stock
Investment in Federal Home Loan Bank stock carried at cost	27,939				37,126				27,939	37,126
Interest income on investment securities
Taxable interest									23,542	29,652	33,390
Nontaxable interest									11,777	5,559	1,222
Dividend income									1,604	446	173
Total interest income on investment securities									36,923	35,657	34,785
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	148,662				67,299				148,662	67,299
Less Than 12 Months, Gross Unrealized Losses	(2,767)				(452)				(2,767)	(452)
12 months or Longer, Carrying Value	32				60				32	60
12 months or Longer, Gross Unrealized Losses	(1)				(1)				(1)	(1)
Total, Carrying Value	148,694				67,359				148,694	67,359
Total, Gross Unrealized Losses	(2,768)				(453)				(2,768)	(453)
Amortized Cost
Total securities available-for-sale	691,944				774,677				691,944	774,677
Carrying Value
Carrying Value	707,188				807,842				707,188	807,842
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	179,938				18,317				179,938	18,317
Less Than 12 Months, Gross Unrealized Losses	(4,486)				(132)				(4,486)	(132)
12 months or Longer, Carrying Value	4,383								4,383
12 months or Longer, Gross Unrealized Losses	(98)								(98)
Total, Carrying Value	184,321				18,317				184,321	18,317
Total, Gross Unrealized Losses	(4,584)				(132)				(4,584)	(132)
Amortized Cost
Total securities available-for-sale	197,069				99,956				197,069	99,956
Carrying Value
Carrying Value	192,873				101,694				192,873	101,694
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	1,640								1,640
Less Than 12 Months, Gross Unrealized Losses	(60)								(60)
12 months or Longer, Carrying Value	617				1,692				617	1,692
12 months or Longer, Gross Unrealized Losses	(90)				(123)				(90)	(123)
Total, Carrying Value	2,257				1,692				2,257	1,692
Total, Gross Unrealized Losses	(150)				(123)				(150)	(123)
Number of securities impaired due to deteriorating cash flows					1					1
OTTI charges									0	1,100	0
FDIC loss sharing income										892
FDIC loss sharing income (as a percent)										80.00%
Amortized Cost
Total securities available-for-sale	30,502				36,078				30,502	36,078
Carrying Value
Carrying Value	37,904				44,684				37,904	44,684
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	337,208				90,303				337,208	90,303
Less Than 12 Months, Gross Unrealized Losses	(24,273)				(1,951)				(24,273)	(1,951)
Total, Carrying Value	337,208				90,303				337,208	90,303
Total, Gross Unrealized Losses	(24,273)				(1,951)				(24,273)	(1,951)
Amortized Cost
Total securities available-for-sale	459,182				339,547				459,182	339,547
Carrying Value
Carrying Value	436,658				348,041				436,658	348,041
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	72,636				16,819				72,636	16,819
Less Than 12 Months, Gross Unrealized Losses	(1,483)				(81)				(1,483)	(81)
Total, Carrying Value	72,636				16,819				72,636	16,819
Total, Gross Unrealized Losses	(1,483)				(81)				(1,483)	(81)
Amortized Cost
Total securities available-for-sale	84,119				42,014				84,119	42,014
Carrying Value
Carrying Value	82,707				42,365				82,707	42,365
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	9,872								9,872
Less Than 12 Months, Gross Unrealized Losses	(174)								(174)
Total, Carrying Value	9,872								9,872
Total, Gross Unrealized Losses	(174)								(174)
Amortized Cost
Total securities available-for-sale	10,046								10,046
Carrying Value
Carrying Value	9,872								9,872
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	23,969								23,969
Less Than 12 Months, Gross Unrealized Losses	(113)								(113)
Total, Carrying Value	23,969								23,969
Total, Gross Unrealized Losses	(113)								(113)
Amortized Cost
Total securities available-for-sale	27,654				6,389				27,654	6,389
Carrying Value
Carrying Value	$ 27,543				$ 10,759				$ 27,543	$ 10,759