GOODWILL AND OTHER INTANGIBLE ASSETS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Sep. 30, 2011
Carrying amounts of goodwill [Roll Forward]
Balance, beginning of period	$ 270,097	$ 270,097
Goodwill recorded during the period	1,200	0
Balance, end of period	271,297	270,097
Amortized intangible assets [Abstract]
Gross Carrying Amount	60,625	60,912
Accumulated Amortization	44,701	41,977
Aggregate amortization expense [Abstract]
Total	3,324	3,909
Estimated Amortization Expense:
For year ending December 31, 2012	2,957
For year ending December 31, 2013	2,268
For year ending December 31, 2014	1,961
For year ending December 31, 2015	1,645
For year ending December 31, 2016	1,344
Trade names [Member]
Unamortized intangible assets [Abstract]
Gross Carrying Amount	688	688
Core deposit intangibles [Member]
Amortized intangible assets [Abstract]
Gross Carrying Amount	27,801	27,801
Accumulated Amortization	20,728	19,716
Aggregate amortization expense [Abstract]
Total	1,012	1,308
Estimated Amortization Expense:
For year ending December 31, 2012	946
For year ending December 31, 2013	582
For year ending December 31, 2014	526
For year ending December 31, 2015	487
For year ending December 31, 2016	451
Customer relationship intangibles [Member]
Amortized intangible assets [Abstract]
Gross Carrying Amount	32,749	32,511
Accumulated Amortization	23,935	21,661
Aggregate amortization expense [Abstract]
Total	2,274	2,601
Estimated Amortization Expense:
For year ending December 31, 2012	1,974
For year ending December 31, 2013	1,686
For year ending December 31, 2014	1,435
For year ending December 31, 2015	1,158
For year ending December 31, 2016	893
Non-solicitation intangibles [Member]
Amortized intangible assets [Abstract]
Gross Carrying Amount	75	600
Accumulated Amortization	38	600
Aggregate amortization expense [Abstract]
Total	38	0
Estimated Amortization Expense:
For year ending December 31, 2012	37
For year ending December 31, 2013	0
For year ending December 31, 2014	0
For year ending December 31, 2015	0
For year ending December 31, 2016	0
Community Banking [Member]
Carrying amounts of goodwill [Roll Forward]
Balance, beginning of period	217,618	217,618
Goodwill recorded during the period	0	0
Balance, end of period	217,618	217,618
Percentage of fair value over carrying value for goodwill impairment analysis (in hundredths)			2.00%
Insurance Agencies [Member]
Carrying amounts of goodwill [Roll Forward]
Balance, beginning of period	52,479	52,479
Goodwill recorded during the period	1,200	0
Balance, end of period	$ 53,679	$ 52,479
Percentage of fair value over carrying value for goodwill impairment analysis (in hundredths)			30.00%