ALLOWANCE FOR CREDIT LOSSES (1) (Details) (USD $)	Jun. 30, 2013	Dec. 31, 2012	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	$ 105,492,000	$ 156,728,000
Allowance for impaired loans and leases	7,965,000	10,541,000
Allowance for all other loans and leases	153,082,000	153,925,000
Total allowance	161,047,000	164,466,000	175,847,000	195,118,000
Evaluated for impairment threshold	500,000
Construction, acquisition and development [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	34,531,000	61,335,000
Allowance for impaired loans and leases	3,373,000	4,350,000
Commercial and industrial segment [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	3,142,000	4,845,000
Allowance for impaired loans and leases	284,000	1,241,000
Allowance for all other loans and leases	23,708,000	22,045,000
Total allowance	23,992,000	23,286,000	25,815,000	20,724,000
Real estate segment [Member] | Consumer mortgages [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	13,636,000	15,107,000
Allowance for impaired loans and leases	525,000	1,103,000
Allowance for all other loans and leases	34,708,000	34,863,000
Total allowance	35,233,000	35,966,000	34,431,000	36,529,000
Real estate segment [Member] | Home equity [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	1,780,000	1,380,000
Allowance for impaired loans and leases	32,000	111,000
Allowance for all other loans and leases	6,163,000	5,894,000
Total allowance	6,195,000	6,005,000	7,336,000	8,630,000
Real estate segment [Member] | Agricultural [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	3,758,000	5,382,000
Allowance for impaired loans and leases	116,000	92,000
Allowance for all other loans and leases	3,108,000	3,209,000
Total allowance	3,224,000	3,301,000	3,259,000	3,921,000
Real estate segment [Member] | Commercial and industrial-owner occupied [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	12,471,000	16,720,000
Allowance for impaired loans and leases	1,268,000	864,000
Allowance for all other loans and leases	19,469,000	19,314,000
Total allowance	20,737,000	20,178,000	17,359,000	21,929,000
Real estate segment [Member] | Construction, acquisition and development [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	34,531,000	61,335,000
Allowance for impaired loans and leases	3,373,000	4,350,000
Allowance for all other loans and leases	16,246,000	17,555,000
Total allowance	19,619,000	21,905,000	32,755,000	45,562,000
Real estate segment [Member] | Commercial real estate [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	35,525,000	50,413,000
Allowance for impaired loans and leases	2,367,000	2,720,000
Allowance for all other loans and leases	34,125,000	37,361,000
Total allowance	36,492,000	40,081,000	37,166,000	39,444,000
Credit cards segment [Member]
Financing Receivable, Impaired [Line Items]
Allowance for all other loans and leases	3,628,000	3,611,000
Total allowance	3,628,000	3,611,000	3,159,000	4,021,000
All other [Member]
Financing Receivable, Impaired [Line Items]
Recorded balance of impaired loans	649,000	1,546,000
Allowance for impaired loans and leases		60,000
Allowance for all other loans and leases	11,927,000	10,073,000
Total allowance	$ 11,927,000	$ 10,133,000	$ 14,567,000	$ 14,358,000