FAIR VALUE (Details) (USD $)	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011
Available-for-sale investment securities [Abstract]
Total available-for-sale investment securities	$ 2,121,394,000		$ 1,538,973,000
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	2,000,000
Discount on appraisal value of foreclosed real estate, minimum (in hundredths)	11.00%
Discount on appraisal value of foreclosed real estate, maximum (in hundredths)	60.00%
Impaired Loans Valuation Allowance	430,000
Level 3 Assets Measured at Fair Value on a Recurring Basis [Abstract]
Beginning balance	43,846,000		42,051,000
Total gains/(losses) included in earnings			(164,000)	[1],[2]
Total gains/(losses) included in other comprehensive income			3,248,000	[3]
Principal reductions			(1,489,000)
Commitments to originate real estate loans held for sale, net			200,000
Ending balance			43,846,000
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Weighted average discount rate Input Range Minimum (in hundredths)	2.50%
Weighted average discount rate Input Range Maximum (in hundredths)	3.30%
Weighted average discount rate Input Range Weighted Average (in hundredths)	3.10%
Adequate Compensation Input Range	$7/loan
Carrying Value [Member]
Financial assets [Abstract]
Net loans	3,865,576,000		3,471,025,000
Financial liabilities [Abstract]
Deposits	5,628,039,000		4,795,245,000
Borrowings	728,061,000		728,281,000
Subordinated debt held by unconsolidated subsidiary trusts	102,073,000		102,048,000
Fair Value [Member]
Financial assets [Abstract]
Net loans	3,881,354,000		3,491,729,000
Financial liabilities [Abstract]
Deposits	5,635,320,000		4,810,856,000
Borrowings	820,377,000		828,018,000
Subordinated debt held by unconsolidated subsidiary trusts	97,899,000		73,211,000
Pooled Trust Preferred Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value of assets classified as Level 3	49,600,000
Pooled trust preferred securities, Valuation Technique	Consensus pricing
Significant Unobservable Inputs, Inputs Description	Weighting of offered quotes
Significant Unobservable Input Range, Minimum (in hundredths)	65.30%
Significant Unobservable Input Range, Maximum (in hundredths)	85.10%
Significant Unobservable Input Range, Weighted Average (in hundredths)	78.40%
Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value of assets classified as Level 3	1,186,000
Impaired loans, Valuation Technique	Fair value of collateral
Significant Unobservable Inputs, Inputs Description	Discount on collateral fair value
Significant Unobservable Input Range, Minimum (in hundredths)	25.00%
Significant Unobservable Input Range, Maximum (in hundredths)	50.00%
Significant Unobservable Input Range, Weighted Average (in hundredths)	27.50%
Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value of assets classified as Level 3	4,788,000
Other real estate owned, Valuation Technique	Fair value of collateral
Significant Unobservable Inputs, Inputs Description	Discount on collateral fair value
Significant Unobservable Input Range, Minimum (in hundredths)	11.00%
Significant Unobservable Input Range, Maximum (in hundredths)	60.20%
Significant Unobservable Input Range, Weighted Average (in hundredths)	19.90%
Mortgage Servicing Rights [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value of assets classified as Level 3	1,028,000
Mortgage servicing rights, Valuation Technique	Discounted cash flow
Significant Unobservable Inputs, Inputs Description	Weighted average constant prepayment rate
Constant Prepayment Input Range Minimum (in hundredths)	1.10%
Constant Prepayment Input Range Maximum (in hundredths)	39.60%
Constant Prepayment Input Range Weighted Average (in hundredths)	34.40%
Pooled Trust Preferred Securities [Member]
Level 3 Assets Measured at Fair Value on a Recurring Basis [Abstract]
Beginning balance	43,846,000		41,993,000
Total gains/(losses) included in earnings	220,000	[1],[2]	94,000	[1],[2]
Total gains/(losses) included in other comprehensive income	11,890,000	[3]	3,248,000	[3]
Principal reductions	(6,356,000)		(1,489,000)
Commitments to originate real estate loans held for sale, net	0		0
Ending balance	49,600,000		43,846,000
Commitments to Originate Real Estate Loans for Sale [Member]
Level 3 Assets Measured at Fair Value on a Recurring Basis [Abstract]
Beginning balance			58,000
Total gains/(losses) included in earnings			(258,000)	[1],[2]
Total gains/(losses) included in other comprehensive income			0	[3]
Principal reductions			0
Commitments to originate real estate loans held for sale, net			200,000
Ending balance			0
Recurring [Member]
Available-for-sale investment securities [Abstract]
U.S. Treasury and agency securities	1,079,257,000		520,548,000
Obligations of state and political subdivisions	662,892,000		573,012,000
Government agency mortgage-backed securities	269,951,000		331,379,000
Pooled trust preferred securities	49,600,000		43,846,000
Government agency collateralized mortgage obligations	33,935,000		46,943,000
Corporate debt securities	25,357,000		22,855,000
Marketable equity securities	402,000		390,000
Total available-for-sale investment securities	2,121,394,000		1,538,973,000
Mortgage loans held for sale			532,000
Total			1,539,505,000
Recurring [Member] | Level 1 [Member]
Available-for-sale investment securities [Abstract]
U.S. Treasury and agency securities	891,803,000		311,958,000
Obligations of state and political subdivisions	0		0
Government agency mortgage-backed securities	0		0
Pooled trust preferred securities	0		0
Government agency collateralized mortgage obligations	0		0
Corporate debt securities	0		0
Marketable equity securities	402,000		390,000
Total available-for-sale investment securities	892,205,000		312,348,000
Mortgage loans held for sale			0
Total			312,348,000
Recurring [Member] | Level 2 [Member]
Available-for-sale investment securities [Abstract]
U.S. Treasury and agency securities	187,454,000		208,590,000
Obligations of state and political subdivisions	662,892,000		573,012,000
Government agency mortgage-backed securities	269,951,000		331,379,000
Pooled trust preferred securities	0		0
Government agency collateralized mortgage obligations	33,935,000		46,943,000
Corporate debt securities	25,357,000		22,855,000
Marketable equity securities	0		0
Total available-for-sale investment securities	1,179,589,000		1,182,779,000
Mortgage loans held for sale			532,000
Total			1,183,311,000
Recurring [Member] | Level 3 [Member]
Available-for-sale investment securities [Abstract]
U.S. Treasury and agency securities	0		0
Obligations of state and political subdivisions	0		0
Government agency mortgage-backed securities	0		0
Pooled trust preferred securities	49,600,000		43,846,000
Government agency collateralized mortgage obligations	0		0
Corporate debt securities	0		0
Marketable equity securities	0		0
Total available-for-sale investment securities	49,600,000		43,846,000
Mortgage loans held for sale			0
Total			43,846,000
Nonrecurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	1,186,000		4,118,000
Other real estate owned	4,788,000		2,682,000
Mortgage servicing rights	1,028,000		1,747,000
Total	7,002,000		8,547,000
Nonrecurring [Member] | Level 1 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	0		0
Other real estate owned	0		0
Mortgage servicing rights	0		0
Total	0		0
Nonrecurring [Member] | Level 2 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	0		0
Other real estate owned	0		0
Mortgage servicing rights	0		0
Total	0		0
Nonrecurring [Member] | Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loans	1,186,000		4,118,000
Other real estate owned	4,788,000		2,682,000
Mortgage servicing rights	1,028,000		1,747,000
Total	$ 7,002,000		$ 8,547,000

[1] Amounts included in earnings associated with the pooled trust preferred securities relate to accretion of related discount and are reported in interest and dividends on taxable investments.

[2] Amounts included in earnings associated with the commitments to originate real estate loans for sale are reported as a component of other banking service fees.

[3] Amounts included in other comprehensive income associated with the pooled trust preferred securities are relate to changes in unrealized loss and are reported as a component of unrealized gains on securities in the Statement of Comprehensive Income.