SEGMENT REPORTING (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Results of Operations [Abstract]
Net interest revenue	$ 98,078	$ 105,610
Provision for credit losses	4,000	10,000	28,000
Net interest revenue, after provision for credit losses	94,078	95,610
Noninterest revenue	71,318	72,360
Noninterest expense	135,371	135,680
Income before income taxes	30,025	32,290
Income tax expense (benefit)	9,220	9,424
Net income	20,805	22,866
Selected Financial Information [Abstract]
Total assets at end of period	13,393,135	13,307,572	13,397,198	[1]
Depreciation and amortization	7,456	7,595
Community Banking [Member]
Results of Operations [Abstract]
Net interest revenue	92,244	99,332
Provision for credit losses	4,101	10,228
Net interest revenue, after provision for credit losses	88,143	89,104
Noninterest revenue	26,507	29,163
Noninterest expense	91,005	96,701
Income before income taxes	23,645	21,566
Income tax expense (benefit)	7,604	6,110
Net income	16,041	15,456
Selected Financial Information [Abstract]
Total assets at end of period	10,082,036	10,164,436
Depreciation and amortization	5,788	5,970
Insurance Agencies [Member]
Results of Operations [Abstract]
Net interest revenue	49	73
Provision for credit losses	0	0
Net interest revenue, after provision for credit losses	49	73
Noninterest revenue	26,530	23,151
Noninterest expense	21,407	18,698
Income before income taxes	5,172	4,526
Income tax expense (benefit)	2,076	1,819
Net income	3,096	2,707
Selected Financial Information [Abstract]
Total assets at end of period	183,918	175,763
Depreciation and amortization	894	874
Corporate and Other [Member]
Results of Operations [Abstract]
Net interest revenue	5,785	6,205
Provision for credit losses	(101)	(228)
Net interest revenue, after provision for credit losses	5,886	6,433
Noninterest revenue	18,281	20,046
Noninterest expense	22,959	20,281
Income before income taxes	1,208	6,198
Income tax expense (benefit)	(460)	1,495
Net income	1,668	4,703
Selected Financial Information [Abstract]
Total assets at end of period	3,127,181	2,967,373
Depreciation and amortization	$ 774	$ 751

[1] Derived from audited financial statements.