INVESTMENT SECURITIES (Details) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Held-to-maturity portfolio [Abstract]
Amortized cost	$ 641,540,000	$ 553,495,000
Gross unrealized gains	71,276,000	64,340,000
Gross unrealized losses	0	0
Estimated fair value	712,816,000	617,835,000
Available-for-sale portfolio [Abstract]
Amortized cost	2,051,431,000	1,453,461,000
Gross unrealized gains	156,963,000	110,211,000
Gross unrealized losses	13,290,000	24,699,000
Total available-for-sale investment securities	2,195,104,000	1,538,973,000
Other Securities [Abstract]
Other investment securities, cost	58,641,000	58,902,000
Other investment securities , estimated fair value	58,641,000	58,902,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	22
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	13
Held-to-maturity securities in unrealized loss positions, number of positions	35
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	14,029,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	55,405,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	69,434,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	61,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	13,229,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	13,290,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions		23
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions		12
Total available-for-sale securities in unrealized loss positions, number of positions		35
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value		9,397,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value		49,896,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value		59,293,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses		190,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses		24,509,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses		24,699,000
Held-to-maturity, Amortized Cost [Abstract]
Held -to-maturity, Amortized Cost, Due in one year or less	19,247,000
Held -to-maturity, Amortized Cost, Due in one to five years	269,744,000
Held -to-maturity, Amortized Cost, Due in five through ten years	244,657,000
Held -to-maturity, Amortized Cost, Due after ten years	83,745,000
Held-to-maturity Securities, Amortized Cost, Subtotal	617,393,000
Held-to-maturity Collateralized Mortgage Obligations, Amortized Cost, without single maturity date	0
Held-to-maturity Mortgage Backed Securities, Amortized Cost, without single maturity date	24,147,000
Held-to-maturity, Amortized Cost	641,540,000
Held-to-maturity, Fair value [Abstract]
Held-to-maturity, Fair value, Due in one year or less	19,616,000
Held-to-maturity, Fair value, Due in one to five years	299,886,000
Held-to-maturity, Fair value, Due in five through ten years	273,315,000
Held-to-maturity, Fair value, Due after ten years	94,393,000
Held-to-maturity Securities, Fair Value, Subtotal	687,210,000
Held-to-maturity Collateralized Mortgage Obligations, Fair Value, without single maturity date	0
Held-to-maturity Mortgage Backed Securities, Amortized Cost, without single maturity date	25,606,000
Held-to-maturity, Fair value	712,816,000
Available-for-sale securities, Amortized Cost [Abstract]
Available-for-sale securities, Amortized Cost, Due in one year or less	40,005,000
Available-for-sale securities, Amortized Cost, Due in one to five years	247,590,000
Available-for-sale securities, Amortized Cost, Due in five through ten years	946,581,000
Available-for-sale securities, Amortized Cost, Due after ten years	513,334,000
Available-for-sale Securities, Amortized Cost, with a single maturity date, Subtotal	1,747,510,000
Available-for-sale government agency collateralized mortgage obligations, amortized cost, without a single maturity date	35,897,000
Available-for-sale government agency mortgage-backed securities, amortized cost, without a single maturity date	267,673,000
Available-for-sale securities, Amortized Cost	2,051,080,000
Available-for-sale securities, Fair value [Abstract]
Available-for-sale securities, Fair value, Due in one year or less	40,831,000
Available-for-sale securities, Fair value, Due in one to five years	268,526,000
Available-for-sale securities, Fair value, Due in five through ten years	1,015,277,000
Available-for-sale securities, Fair value, Due after ten years	544,826,000
Available-for-sale Securities, Fair Value, Subtotal	1,869,460,000
Available-for-sale government agency collateralized mortgage obligations, fair value, without single maturity date	36,975,000
Available-for-sale government agency mortgage-backed securities, fair value, without single maturity date	288,295,000
Available-for-sale securities, Fair value	2,194,730,000
Pooled trust preferred, class A-1 securities, par value	65,300,000
Pooled trust preferred, class A-1 securities, unrealized losses	13,100,000
Percentage minimum for underlying collateral to be in deferral or default concurrently before non-receipt of contractual cash flows (in hundredths)	38.00%
Percentage maximum for underlying collateral to be in deferral or default concurrently before non-receipt of contractual cash flows (in hundredths)	42.00%
US Treasury and Agency Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	547,962,000	448,260,000
Gross unrealized gains	63,606,000	56,800,000
Gross unrealized losses	0	0
Estimated fair value	611,568,000	505,060,000
Available-for-sale portfolio [Abstract]
Amortized cost	986,602,000	463,922,000
Gross unrealized gains	99,151,000	56,626,000
Gross unrealized losses	0	0
Total available-for-sale investment securities	1,085,753,000	520,548,000
Obligations of State and Political Subdivisions [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	66,484,000	69,623,000
Gross unrealized gains	6,155,000	5,088,000
Gross unrealized losses	0	0
Estimated fair value	72,639,000	74,711,000
Available-for-sale portfolio [Abstract]
Amortized cost	672,775,000	543,527,000
Gross unrealized gains	34,587,000	29,721,000
Gross unrealized losses	41,000	236,000
Total available-for-sale investment securities	707,321,000	573,012,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	19
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	1
Held-to-maturity securities in unrealized loss positions, number of positions	20
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	10,679,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	562,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	11,241,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	41,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	0
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	41,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions		2
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions		6
Total available-for-sale securities in unrealized loss positions, number of positions		8
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value		211,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value		6,038,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value		6,249,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses		0
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses		236,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses		236,000
Government Agency Mortgage-Backed Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	24,147,000	35,576,000
Gross unrealized gains	1,459,000	2,452,000
Gross unrealized losses	0	0
Estimated fair value	25,606,000	38,028,000
Available-for-sale portfolio [Abstract]
Amortized cost	267,673,000	310,541,000
Gross unrealized gains	20,622,000	20,840,000
Gross unrealized losses	0	2,000
Total available-for-sale investment securities	288,295,000	331,379,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions		3
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions		0
Total available-for-sale securities in unrealized loss positions, number of positions		3
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value		2,415,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value		0
Available-for-sale Securities, Unrealized Loss Position, Fair Value		2,415,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses		2,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses		0
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses		2,000
Pooled Trust Preferred Securities [Member]
Available-for-sale portfolio [Abstract]
Amortized cost	63,970,000	68,115,000
Gross unrealized gains	0	0
Gross unrealized losses	13,133,000	24,269,000
Total available-for-sale investment securities	50,837,000	43,846,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	0
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	3
Held-to-maturity securities in unrealized loss positions, number of positions	3
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	0
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	50,837,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	50,837,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	0
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	13,133,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	13,133,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions		0
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions		3
Total available-for-sale securities in unrealized loss positions, number of positions		3
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value		0
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value		43,846,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value		43,846,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses		0
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses		24,269,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses		24,269,000
Corporate Debt Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	2,929,000	0
Gross unrealized gains	56,000	0
Gross unrealized losses	0	0
Estimated fair value	2,985,000	0
Available-for-sale portfolio [Abstract]
Amortized cost	24,163,000	21,495,000
Gross unrealized gains	1,403,000	1,360,000
Gross unrealized losses	17,000	0
Total available-for-sale investment securities	25,549,000	22,855,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	1
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	0
Held-to-maturity securities in unrealized loss positions, number of positions	1
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	2,947,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	0
Held-to-maturity securities, Unrealized Loss Position, Fair Value	2,947,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	17,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	0
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	17,000
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale portfolio [Abstract]
Amortized cost	35,897,000	45,481,000
Gross unrealized gains	1,116,000	1,572,000
Gross unrealized losses	38,000	110,000
Total available-for-sale investment securities	36,975,000	46,943,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	2
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	8
Held-to-maturity securities in unrealized loss positions, number of positions	10
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	403,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	3,866,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	4,269,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	3,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	35,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	38,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions		17
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions		0
Total available-for-sale securities in unrealized loss positions, number of positions		17
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value		6,648,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value		0
Available-for-sale Securities, Unrealized Loss Position, Fair Value		6,648,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses		110,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses		0
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses		110,000
Marketable Equity Security [Member]
Available-for-sale portfolio [Abstract]
Amortized cost	351,000	380,000
Gross unrealized gains	84,000	92,000
Gross unrealized losses	61,000	82,000
Total available-for-sale investment securities	374,000	390,000
Held-to-maturity securities in unrealized loss positions, number of positions [Abstract]
Held-to-maturity securities in unrealized loss positions for less than 12 months, number of positions	0
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	1
Held-to-maturity securities in unrealized loss positions, number of positions	1
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	0
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	140,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	140,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	0
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	61,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	61,000
Available-for-sale securities in unrealized loss positions, number of positions [Abstract]
Available-for-sale securities in unrealized loss positions for less than 12 months, number of positions		1
Available-for-sale securities in unrealized loss positions for more than 12 months, number of positions		3
Total available-for-sale securities in unrealized loss positions, number of positions		4
Available-for-sale securities, Debt maturities, Fair value [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Fair Value		123,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Fair Value		12,000
Available-for-sale Securities, Unrealized Loss Position, Fair Value		135,000
Available-for-sale securities, Debt maturities, Gross unrealized losses [Abstract]
Available-for-sale Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses		78,000
Available-for-sale Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses		4,000
Available-for-sale Securities, Unrealized Loss Position, Gross unrealized losses		82,000
Federal Reserve Bank Stock [Member]
Other Securities [Abstract]
Other investment securities, cost	15,451,000	15,451,000
Other investment securities , estimated fair value	15,451,000	15,451,000
Federal Home Loan Bank Stock [Member]
Other Securities [Abstract]
Other investment securities, cost	38,113,000	38,343,000
Other investment securities , estimated fair value	38,113,000	38,343,000
Other Equity Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	18,000	36,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated fair value	18,000	36,000
Other Securities [Abstract]
Other investment securities, cost	5,077,000	5,108,000
Other investment securities , estimated fair value	$ 5,077,000	$ 5,108,000