INCOME TAXES (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010		Dec. 31, 2009
Allocation of income taxes [Abstract]
Income tax expense (benefit)	$ 4,475,000	$ (8,705,000)		$ 30,105,000
Shareholders' equity for other comprehensive income	7,600,000	(3,763,000)		11,469,000
Shareholders' equity for stock option plans	(7,000)	(44,000)		(500,000)
Total	12,068,000	(12,512,000)		41,074,000
Current:
Federal	5,643,000	8,865,000		35,936,000
State	5,400,000	(1,520,000)		3,527,000
Deferred:
Federal	(1,626,000)	(13,848,000)		(8,302,000)
State	(4,942,000)	(2,202,000)		(1,056,000)
Total	4,475,000	(8,705,000)		30,105,000
Statutory federal income tax rate (in hundredths)	35.00%	35.00%		35.00%
Income tax reconciliation [Abstract]
Tax expense at statutory rates	14,715,000	4,983,000		39,492,000
Increase (decrease) in taxes resulting from:
State income taxes, net of federal tax benefit	266,000	(2,419,000)		1,606,000
Tax-exempt interest revenue	(7,881,000)	(6,605,000)		(6,105,000)
Tax-exempt earnings on life insurance	(2,647,000)	(2,659,000)		(2,970,000)
Deductible dividends paid on 401(k) plan	(331,000)	(1,972,000)		(1,875,000)
Other, net	353,000	(33,000)		(43,000)
Total	4,475,000	(8,705,000)		30,105,000
Deferred tax assets:
Loans, principally due to allowance for credit losses	73,911,000	75,514,000	[1]
Other real estate owned	10,429,000	5,681,000	[1]
Mark to market - securities	4,165,000	4,216,000	[1]
Accrued liabilities, principally due to compensation arrangements and vacation accruals	10,681,000	9,353,000	[1]
Other	312,000	1,760,000	[1]
State tax credits (net of federal benefit)	1,040,000	0	[1]
Unrecognized pension expense	26,428,000	17,262,000	[1]
Total gross deferred tax assets	126,966,000	113,786,000	[1]
Less: valuation allowance	0	0	[1]
Deferred tax assets	126,966,000	113,786,000	[1]
Deferred tax liabilities:
Lease transactions	37,509,000	32,809,000	[1]
Employment benefits	26,991,000	29,514,000	[1]
Premises and equipment, principally due to differences in depreciation and lease transactions	27,221,000	24,033,000	[1]
Mortgage servicing rights	11,405,000	14,785,000	[1]
Intangible assets	10,336,000	10,080,000	[1]
Investments, principally due to interest income recognition	147,000	4,069,000	[1]
Deferred loan points	2,656,000	2,821,000	[1]
Other assets, principally due to expense recognition	525,000	1,233,000	[1]
Unrealized net losses on available-for-sale securities	25,064,000	8,297,000	[1]
Total gross deferred tax liabilities	141,854,000	127,641,000	[1]
Net deferred tax liabilities	(14,888,000)	(13,855,000)	[1]
Deferred state tax asset	1,040,000
Activity in unrecognized tax benefits [Roll Forward]
Unrecognized tax benefit, January 1	355,000	355,000		355,000
Gross increases - tax positions in prior period	873,000	0		0
Gross decreases - tax positions in prior period	(355,000)	0		0
Gross increases - tax positions in current period	229,000	0		0
Settlements	0	0		0
Lapse of statute of limitations	0	0		0
Unrecognized tax benefit, December 31	1,102,000	355,000		355,000
Tax benefits that, if recognized, would affect the effective tax rate	1,100,000	355,000		355,000
Interest related to unrecognized tax benefits	26,000	28,000		28,000
Liability for interest	$ 231,000	$ 191,000

[1] Certain 2010 amounts have been reclassified to agree with the 2011 presentation.