ALLOWANCE FOR CREDIT LOSSES (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			$ 164,466	$ 195,118	$ 195,118
Charge-offs			(21,992)	(50,726)	(89,398)
Recoveries			11,573	15,455	30,746
Provision	3,000	6,000	7,000	16,000	28,000
Balance at end of period	161,047	175,847	161,047	175,847	164,466
Commercial and industrial segment [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			23,286	20,724	20,724
Charge-offs			(2,946)	(5,854)	(12,362)
Recoveries			1,336	2,582	7,096
Provision			2,316	8,363	7,828
Balance at end of period	23,992	25,815	23,992	25,815	23,286
Real estate segment [Member] | Consumer mortgages [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			35,966	36,529	36,529
Charge-offs			(4,728)	(7,034)	(13,122)
Recoveries			1,816	761	1,836
Provision			2,179	4,175	10,723
Balance at end of period	35,233	34,431	35,233	34,431	35,966
Real estate segment [Member] | Home equity [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			6,005	8,630	8,630
Charge-offs			(803)	(1,387)	(2,721)
Recoveries			444	393	496
Provision			549	(300)	(400)
Balance at end of period	6,195	7,336	6,195	7,336	6,005
Real estate segment [Member] | Agricultural [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			3,301	3,921	3,921
Charge-offs			(329)	(482)	(1,240)
Recoveries			133	63	126
Provision			119	(243)	494
Balance at end of period	3,224	3,259	3,224	3,259	3,301
Real estate segment [Member] | Commercial and industrial-owner occupied [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			20,178	21,929	21,929
Charge-offs			(1,130)	(6,600)	(9,015)
Recoveries			1,693	1,865	2,696
Provision			(4)	165	4,568
Balance at end of period	20,737	17,359	20,737	17,359	20,178
Real estate segment [Member] | Construction, acquisition and development [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			21,905	45,562	45,562
Charge-offs			(3,234)	(20,954)	(33,085)
Recoveries			1,246	4,110	8,407
Provision			(298)	4,037	1,021
Balance at end of period	19,619	32,755	19,619	32,755	21,905
Real estate segment [Member] | Commercial real estate [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			40,081	39,444	39,444
Charge-offs			(6,861)	(6,069)	(12,728)
Recoveries			3,973	4,887	8,538
Provision			(701)	(1,096)	4,827
Balance at end of period	36,492	37,166	36,492	37,166	40,081
Credit cards segment [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			3,611	4,021	4,021
Charge-offs			(1,007)	(1,150)	(2,221)
Recoveries			332	239	527
Provision			692	49	1,284
Balance at end of period	3,628	3,159	3,628	3,159	3,611
All other [Member]
Changes in the allowance for credit losses [Roll Forward]
Balance at beginning of period			10,133	14,358	14,358
Charge-offs			(954)	(1,196)	(2,904)
Recoveries			600	555	1,024
Provision			2,148	850	(2,345)
Balance at end of period	$ 11,927	$ 14,567	$ 11,927	$ 14,567	$ 10,133