LOANS AND LEASES, Troubled Debt Restructurings (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2011
Financial effects of TDRs [Abstract]
Number of Contracts	49	136
Pre-Modification Outstanding Recorded Investment	$ 17,909,000	$ 68,964,000
Post-Modification Outstanding Recorded Investment	17,171,000	58,697,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts	13	34
Recorded Investment	3,693,000	13,004,000
Financing Receivable, Impaired [Line Items]
Recorded Investment in Impaired Loans	211,112,000	234,923,000
Related Allowance for Credit Losses	25,546,000	39,708,000
Average Recorded Investment	224,669,000	309,604,000
Impaired loans [Abstract]
Impaired loans that were characterized as troubled debt restructurings	51,900,000	58,000,000
With no related allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment in Impaired Loans	120,963,000	117,217,000
Related Allowance for Credit Losses	0	0
Average Recorded Investment	105,722,000	167,615,000
With an allowance [Member]
Financing Receivable, Impaired [Line Items]
Recorded Investment in Impaired Loans	90,149,000	117,706,000
Related Allowance for Credit Losses	25,546,000	39,708,000
Average Recorded Investment	118,947,000	141,989,000
Commercial and industrial segment [Member]
Financial effects of TDRs [Abstract]
Number of Contracts	5	7
Pre-Modification Outstanding Recorded Investment	1,010,000	3,142,000
Post-Modification Outstanding Recorded Investment	674,000	2,374,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts	1	4
Recorded Investment	129,000	1,506,000
Real estate segment [Member] | Consumer mortgages [Member]
Financial effects of TDRs [Abstract]
Number of Contracts	13	35
Pre-Modification Outstanding Recorded Investment	3,265,000	6,901,000
Post-Modification Outstanding Recorded Investment	3,211,000	6,424,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts	6	4
Recorded Investment	518,000	1,563,000
Real estate segment [Member] | Agricultural [Member]
Financial effects of TDRs [Abstract]
Number of Contracts	1	4
Pre-Modification Outstanding Recorded Investment	407,000	2,650,000
Post-Modification Outstanding Recorded Investment	404,000	1,479,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts	1	3
Recorded Investment	170,000	1,382,000
Real estate segment [Member] | Commercial and industrial-owner occupied [Member]
Financial effects of TDRs [Abstract]
Number of Contracts	8	29
Pre-Modification Outstanding Recorded Investment	2,128,000	13,330,000
Post-Modification Outstanding Recorded Investment	2,117,000	11,740,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts	3	6
Recorded Investment	1,362,000	1,683,000
Real estate segment [Member] | Construction, acquisition and development [Member]
Financial effects of TDRs [Abstract]
Number of Contracts	11	30
Pre-Modification Outstanding Recorded Investment	7,280,000	23,863,000
Post-Modification Outstanding Recorded Investment	6,956,000	19,228,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts		13
Recorded Investment		3,622,000
Real estate segment [Member] | Commercial [Member]
Financial effects of TDRs [Abstract]
Number of Contracts	6	24
Pre-Modification Outstanding Recorded Investment	3,180,000	16,121,000
Post-Modification Outstanding Recorded Investment	3,172,000	15,046,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts	2	3
Recorded Investment	1,514,000	2,946,000
All other receivables [Member]
Financial effects of TDRs [Abstract]
Number of Contracts	5	7
Pre-Modification Outstanding Recorded Investment	639,000	2,957,000
Post-Modification Outstanding Recorded Investment	637,000	2,406,000
TDRs modified for which there was a payment default [Abstract]
Number of Contracts		1
Recorded Investment		$ 302,000