ALLOWANCE FOR CREDIT LOSSES (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	$ 195,118	$ 196,913	$ 176,043
Provision for credit losses	28,000	130,081	204,016
Recoveries	30,746	10,179	7,876
Loans and leases charged off	(89,398)	(142,055)	(191,022)
Balance at end of year	164,466	195,118	196,913
Commercial and industrial segment [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	20,724	22,479
Provision for credit losses	7,828	14,015
Recoveries	7,096	1,567
Loans and leases charged off	(12,362)	(17,337)
Balance at end of year	23,286	20,724
Real estate segment [Member] | Consumer mortgages [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	36,529	35,540
Provision for credit losses	10,723	10,064
Recoveries	1,836	1,111
Loans and leases charged off	(13,122)	(10,186)
Balance at end of year	35,966	36,529
Real estate segment [Member] | Home equity [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	8,630	7,305
Provision for credit losses	(400)	6,992
Recoveries	496	185
Loans and leases charged off	(2,721)	(5,852)
Balance at end of year	6,005	8,630
Real estate segment [Member] | Agricultural [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	3,921	4,997
Provision for credit losses	494	2,221
Recoveries	126	123
Loans and leases charged off	(1,240)	(3,420)
Balance at end of year	3,301	3,921
Real estate segment [Member] | Commercial and industrial-owner occupied [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	21,929	20,403
Provision for credit losses	4,568	11,435
Recoveries	2,696	393
Loans and leases charged off	(9,015)	(10,302)
Balance at end of year	20,178	21,929
Real estate segment [Member] | Construction, acquisition and development [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	45,562	59,048
Provision for credit losses	1,021	49,925
Recoveries	8,407	3,951
Loans and leases charged off	(33,085)	(67,362)
Balance at end of year	21,905	45,562
Real estate segment [Member] | Commercial [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	39,444	33,439
Provision for credit losses	4,827	22,396
Recoveries	8,538	1,045
Loans and leases charged off	(12,728)	(17,436)
Balance at end of year	40,081	39,444
Credit cards segment [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	4,021	4,126
Provision for credit losses	1,284	2,164
Recoveries	527	803
Loans and leases charged off	(2,221)	(3,072)
Balance at end of year	3,611	4,021
All other receivables [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period	14,358	9,576
Provision for credit losses	(2,345)	10,869
Recoveries	1,024	1,001
Loans and leases charged off	(2,904)	(7,088)
Balance at end of year	$ 10,133	$ 14,358