FAIR VALUE (Details) (USD $)	3 Months Ended
Mar. 31, 2014	Dec. 31, 2013
Available-for-sale investment securities:
Total available-for-sale investment securities	$ 2,470,286,000	$ 2,186,163,000
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Discount on appraisal value of foreclosed real estate, minimum (in hundredths)	5.00%
Discount on appraisal value of foreclosed real estate, maximum (in hundredths)	69.00%
Fair value of MSRs at end of period	1,600,000
Carrying value before valuation allowance at end of period	1,100,000
Mortgage Servicing Rights, Valuation Allowance	0
Recurring [Member]
Available-for-sale investment securities:
U.S. Treasury and agency securities	1,466,731,000	1,212,147,000
Obligations of state and political subdivisions	699,126,000	668,982,000
Government agency mortgage-backed securities	254,850,000	254,978,000
Corporate debt securities	27,557,000	27,587,000
Government agency collateralized mortgage obligations	21,589,000	22,048,000
Marketable equity securities	433,000	421,000
Total available-for-sale investment securities	2,470,286,000	2,186,163,000
Mortgages loans held for sale	802,000	728,000
Commitments to originate real estate loans for sale	67,000	44,000
Forward sales commitments	9,000	27,000
Total	2,471,164,000	2,186,962,000
Recurring [Member] \| Level 1 [Member]
Available-for-sale investment securities:
U.S. Treasury and agency securities	1,437,219,000	1,182,261,000
Obligations of state and political subdivisions	0	0
Government agency mortgage-backed securities	0	0
Corporate debt securities	0	0
Government agency collateralized mortgage obligations	0	0
Marketable equity securities	433,000	421,000
Total available-for-sale investment securities	1,437,652,000	1,182,682,000
Mortgages loans held for sale	0	0
Commitments to originate real estate loans for sale	0	0
Forward sales commitments	0	0
Total	1,437,652,000	1,182,682,000
Recurring [Member] \| Level 2 [Member]
Available-for-sale investment securities:
U.S. Treasury and agency securities	29,512,000	29,886,000
Obligations of state and political subdivisions	699,126,000	668,982,000
Government agency mortgage-backed securities	254,850,000	254,978,000
Corporate debt securities	27,557,000	27,587,000
Government agency collateralized mortgage obligations	21,589,000	22,048,000
Marketable equity securities	0	0
Total available-for-sale investment securities	1,032,634,000	1,003,481,000
Mortgages loans held for sale	802,000	728,000
Commitments to originate real estate loans for sale	0	0
Forward sales commitments	9,000	27,000
Total	1,033,445,000	1,004,236,000
Mortgage loans held for sale, at principal value	800,000
Mortgage loans held for sale, Unrealized gains (losses)	20,000
Recurring [Member] \| Level 3 [Member]
Available-for-sale investment securities:
U.S. Treasury and agency securities	0	0
Obligations of state and political subdivisions	0	0
Government agency mortgage-backed securities	0	0
Corporate debt securities	0	0
Government agency collateralized mortgage obligations	0	0
Marketable equity securities	0	0
Total available-for-sale investment securities	0	0
Mortgages loans held for sale	0	0
Commitments to originate real estate loans for sale	67,000	44,000
Forward sales commitments	0	0
Total	67,000	44,000
Nonrecurring [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loan balance	420,000	600,000
Other real estate owned	4,914,000	5,060,000
Total	5,334,000	5,660,000
Nonrecurring [Member] \| Level 1 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loan balance	0	0
Other real estate owned	0	0
Total	0	0
Nonrecurring [Member] \| Level 2 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loan balance	0	600,000
Other real estate owned	0	0
Total	0	600,000
Nonrecurring [Member] \| Level 3 [Member]
Assets and Liabilities Measured on Nonrecurring Basis [Abstract]
Impaired loan balance	420,000	0
Other real estate owned	4,914,000	5,060,000
Total	$ 5,334,000	$ 5,060,000

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents debt securities issued by corporations.

No definition available.