ALLOWANCE FOR CREDIT LOSSES (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			$ 195,118	$ 196,913	$ 196,913
Charge-offs			(69,674)	(115,615)	(142,055)
Recoveries			21,575	7,557	10,179
Provision	6,000	25,112	22,000	110,831	130,081
Balance at end of year	169,019	199,686	169,019	199,686	195,118
Commercial and industrial segment [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			20,724	22,479	22,479
Charge-offs			(10,188)	(15,660)	(17,337)
Recoveries			3,589	1,121	1,567
Provision			7,580	12,084	14,015
Balance at end of year	21,705	20,024	21,705	20,024	20,724
Real estate [Member] | Consumer mortgages [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			36,529	35,540	35,540
Charge-offs			(9,333)	(7,233)	(10,186)
Recoveries			1,017	848	1,111
Provision			3	10,346	10,064
Balance at end of year	28,216	39,501	28,216	39,501	36,529
Real estate [Member] | Home equity [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			8,630	7,305	7,305
Charge-offs			(1,657)	(4,185)	(5,852)
Recoveries			430	142	185
Provision			(1,482)	6,626	6,992
Balance at end of year	5,921	9,888	5,921	9,888	8,630
Real estate [Member] | Agricultural [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			3,921	4,997	4,997
Charge-offs			(784)	(3,310)	(3,420)
Recoveries			116	47	123
Provision			(599)	2,658	2,221
Balance at end of year	2,654	4,392	2,654	4,392	3,921
Real estate [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	20,403
Charge-offs			(7,594)	(9,166)	(10,302)
Recoveries			2,135	293	393
Provision			2,849	9,940	11,435
Balance at end of year	19,319	21,470	19,319	21,470	21,929
Real estate [Member] | Construction, acquisition and development [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			45,562	59,048	59,048
Charge-offs			(27,799)	(56,823)	(67,362)
Recoveries			6,786	2,980	3,951
Provision			7,993	43,033	49,925
Balance at end of year	32,542	48,238	32,542	48,238	45,562
Real estate [Member] | Commercial Real Estate [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			39,444	33,439	33,439
Charge-offs			(8,702)	(10,578)	(17,436)
Recoveries			6,330	705	1,045
Provision			5,099	15,997	22,396
Balance at end of year	42,171	39,563	42,171	39,563	39,444
Credit cards segment [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			4,021	4,126	4,126
Charge-offs			(1,690)	(2,366)	(3,072)
Recoveries			383	635	803
Provision			455	1,525	2,164
Balance at end of year	3,169	3,920	3,169	3,920	4,021
All other receivables [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			14,358	9,576	9,576
Charge-offs			(1,927)	(6,294)	(7,088)
Recoveries			789	786	1,001
Provision			102	8,622	10,869
Balance at end of year	$ 13,322	$ 12,690	$ 13,322	$ 12,690	$ 14,358