FAIR VALUE MEASUREMENTS (Details 5) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Financial Assets
Securities available for sale	$ 558,875,000	$ 466,169,000
Derivative assets	13,269,000	14,746,000
Financial Liabilities
Derivative liabilities	(26,562,000)	(29,814,000)
Unrealized losses on forward commitments	500,000	1,300,000
Methods and assumptions used to estimate the fair value of significant classes of financial instruments
Junior subordinated debentures re-price period	90 days
Level 1
Financial Assets
Cash and cash equivalents	53,683,000	63,382,000
Securities available for sale	31,130,000	25,291,000
Financial Liabilities
Derivative liabilities	33,000	282,000
Level 2
Financial Assets
Securities available for sale	526,077,000	439,993,000
Restricted equity securities	37,870,000	39,785,000
Loans held for sale	72,348,000	85,368,000
Accrued interest receivable	12,368,000	14,731,000
Cash surrender value of bank-owned life insurance policies	88,893,000	88,198,000
Derivative assets	13,269,000	14,746,000
Financial Liabilities
Total deposits	4,110,772,000	4,116,999,000
Short-term debt	114,644,000	163,150,000
Long-term Federal Home Loan Bank advances	198,591,000	199,420,000
Junior subordinated notes	88,589,000	73,967,000
Derivative liabilities	26,562,000	29,818,000
Level 3
Financial Assets
Trading security	16,485,000	16,893,000
Securities available for sale	1,668,000	885,000
Securities held to maturity	51,634,000	51,024,000
Net loans	3,917,205,000	4,044,259,000
Derivative assets	2,758,000	6,258,000
Financial Liabilities
Derivative liabilities	517,000	1,055,000
Carrying Amount
Financial Assets
Cash and cash equivalents	53,683,000	63,382,000
Trading security	16,485,000	16,893,000
Securities available for sale	558,875,000	466,169,000
Securities held to maturity	50,472,000	51,024,000
Restricted equity securities	37,870,000	39,785,000
Net loans	3,855,809,000	3,955,446,000
Loans held for sale	72,348,000	85,368,000
Accrued interest receivable	12,368,000	14,731,000
Cash surrender value of bank-owned life insurance policies	88,893,000	88,198,000
Derivative assets	16,027,000	21,004,000
Financial Liabilities
Total deposits	4,100,591,000	4,104,402,000
Short-term debt	114,390,000	163,150,000
Long-term Federal Home Loan Bank advances	195,208,000	195,321,000
Junior subordinated notes	89,632,000	89,617,000
Derivative liabilities	27,112,000	31,155,000
Fair Value
Financial Assets
Cash and cash equivalents	53,683,000	63,382,000
Trading security	16,485,000	16,893,000
Securities available for sale	558,875,000	466,169,000
Securities held to maturity	51,634,000	51,024,000
Restricted equity securities	37,870,000	39,785,000
Net loans	3,917,205,000	4,004,259,000
Loans held for sale	72,348,000	85,368,000
Accrued interest receivable	12,368,000	14,731,000
Cash surrender value of bank-owned life insurance policies	88,893,000	88,198,000
Derivative assets	16,027,000	21,004,000
Financial Liabilities
Total deposits	4,110,772,000	4,116,999,000
Short-term debt	114,644,000	163,150,000
Long-term Federal Home Loan Bank advances	198,591,000	199,420,000
Junior subordinated notes	88,589,000	73,967,000
Derivative liabilities	$ 27,112,000	$ 31,155,000