LOANS AND LEASES, Aging (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	$ 24,473	$ 29,315
60-89 Days Past Due	10,231	11,524
90 Plus Days Past Due	48,950	51,345
Total Past Due	83,654	92,184
Current	8,497,884	8,544,805
Total	8,581,538	8,636,989
90 Plus Days Past Due still Accruing	1,125	1,210	1,698
Commercial and industrial segment [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	1,704	3,531
60-89 Days Past Due	145	476
90 Plus Days Past Due	2,188	4,118
Total Past Due	4,037	8,125
Current	1,476,879	1,468,486
Total	1,480,916	1,476,611
90 Plus Days Past Due still Accruing	22	414
Real estate segment [Member] | Consumer mortgages [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	12,110	11,308
60-89 Days Past Due	2,535	3,643
90 Plus Days Past Due	15,155	13,821
Total Past Due	29,800	28,772
Current	1,841,512	1,845,103
Total	1,871,312	1,873,875
90 Plus Days Past Due still Accruing	842	512
Real estate segment [Member] | Home equity [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	2,429	1,337
60-89 Days Past Due	1,208	371
90 Plus Days Past Due	377	350
Total Past Due	4,014	2,058
Current	478,384	484,016
Total	482,398	486,074
90 Plus Days Past Due still Accruing	0	0
Real estate segment [Member] | Agricultural [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	756	400
60-89 Days Past Due	170	287
90 Plus Days Past Due	3,284	3,946
Total Past Due	4,210	4,633
Current	245,257	251,563
Total	249,467	256,196
90 Plus Days Past Due still Accruing	0	10
Real estate segment [Member] | Commercial and industrial-owner occupied [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	1,234	2,629
60-89 Days Past Due	1,509	3,587
90 Plus Days Past Due	2,951	2,933
Total Past Due	5,694	9,149
Current	1,329,280	1,323,954
Total	1,334,974	1,333,103
90 Plus Days Past Due still Accruing	0	19
Real estate segment [Member] | Construction, acquisition and development [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	2,965	2,547
60-89 Days Past Due	4,007	2,472
90 Plus Days Past Due	12,329	14,790
Total Past Due	19,301	19,809
Current	708,791	715,999
Total	728,092	735,808
90 Plus Days Past Due still Accruing	0	0
Real estate segment [Member] | Commercial real estate [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	1,613	4,673
60-89 Days Past Due	58	56
90 Plus Days Past Due	11,764	10,469
Total Past Due	13,435	15,198
Current	1,726,098	1,733,683
Total	1,739,533	1,748,881
90 Plus Days Past Due still Accruing	0	0
Credit cards segment [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	420	536
60-89 Days Past Due	266	379
90 Plus Days Past Due	492	473
Total Past Due	1,178	1,388
Current	97,625	103,496
Total	98,803	104,884
90 Plus Days Past Due still Accruing	261	228
All other [Member]
Aging of loan and lease portfolio [Abstract]
30-59 Days Past Due	1,242	2,354
60-89 Days Past Due	333	253
90 Plus Days Past Due	410	445
Total Past Due	1,985	3,052
Current	594,058	618,505
Total	596,043	621,557
90 Plus Days Past Due still Accruing	$ 0	$ 27