INVESTMENT SECURITIES (Details) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Held-to-maturity portfolio [Abstract]
Amortized cost	$ 647,747,000	$ 553,495,000
Gross unrealized gains	69,432,000	64,340,000
Gross unrealized losses	0	0
Estimated fair value	717,179,000	617,835,000
Available-for-sale portfolio [Abstract]
Amortized cost	2,076,249,000	1,453,461,000
Gross unrealized gains	147,375,000	110,211,000
Gross unrealized losses	17,477,000	24,699,000
Total available-for-sale investment securities	2,206,147,000	1,538,973,000
Other Securities [Abstract]
Other investment securities, cost	78,024,000	58,902,000
Other investment securities , estimated fair value	78,024,000	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	162
Held-to-maturity securities in unrealized loss positions 12 months or more, number of positions	17
Held-to-maturity securities in unrealized loss positions, number of positions	179
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	115,369,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	53,945,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	169,314,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	1,512,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	15,965,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	17,477,000
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	22,134,000
Held -to-maturity, Amortized Cost, Due in one to five years	270,054,000
Held -to-maturity, Amortized Cost, Due in five through ten years	164,044,000
Held -to-maturity, Amortized Cost, Due after ten years	163,693,000
Held-to-maturity Securities, Amortized Cost, Subtotal	619,925,000
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	27,822,000
Held-to-maturity, Amortized Cost	647,747,000
Held-to-maturity, Fair value [Abstract]
Held-to-maturity, Fair value, Due in one year or less	22,631,000
Held-to-maturity, Fair value, Due in one to five years	299,848,000
Held-to-maturity, Fair value, Due in five through ten years	187,712,000
Held-to-maturity, Fair value, Due after ten years	177,497,000
Held-to-maturity Securities, Fair Value, Subtotal	687,688,000
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	29,491,000
Held-to-maturity, Fair value	717,179,000
Available-for-sale securities, Amortized Cost [Abstract]
Available-for-sale securities, Amortized Cost, Due in one year or less	31,757,000
Available-for-sale securities, Amortized Cost, Due in one to five years	226,808,000
Available-for-sale securities, Amortized Cost, Due in five through ten years	979,205,000
Available-for-sale securities, Amortized Cost, Due after ten years	521,414,000
Available-for-sale Securities, Amortized Cost, with a single maturity date, Subtotal	1,759,184,000
Available-for-sale government agency collateralized mortgage obligations, amortized cost, without a single maturity date	38,713,000
Available-for-sale government agency mortgage-backed securities, amortized cost, without a single maturity date	277,971,000
Available-for-sale securities, Amortized Cost	2,075,868,000
Available-for-sale securities, Fair value [Abstract]
Available-for-sale securities, Fair value, Due in one year or less	32,476,000
Available-for-sale securities, Fair value, Due in one to five years	243,177,000
Available-for-sale securities, Fair value, Due in five through ten years	1,046,438,000
Available-for-sale securities, Fair value, Due after ten years	545,450,000
Available-for-sale Securities, Fair Value, Subtotal	1,867,541,000
Available-for-sale government agency collateralized mortgage obligations, fair value, without single maturity date	39,910,000
Available-for-sale government agency mortgage-backed securities, fair value, without single maturity date	298,314,000
Available-for-sale securities, Fair value	2,205,765,000
Pooled trust preferred, class A-1 securities, par value	66,100,000
Pooled trust preferred, class A-1 securities, unrealized losses	15,900,000
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)	40.00%
US Treasury and Agency Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	547,294,000	448,260,000
Gross unrealized gains	62,053,000	56,800,000
Gross unrealized losses	0	0
Estimated fair value	609,347,000	505,060,000
Available-for-sale portfolio [Abstract]
Amortized cost	994,415,000	463,922,000
Gross unrealized gains	94,877,000	56,626,000
Gross unrealized losses	0	0
Total available-for-sale investment securities	1,089,292,000	520,548,000
Obligations of State and Political Subdivisions [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	69,669,000	69,623,000
Gross unrealized gains	5,707,000	5,088,000
Gross unrealized losses	0	0
Estimated fair value	75,376,000	74,711,000
Available-for-sale portfolio [Abstract]
Amortized cost	685,086,000	543,527,000
Gross unrealized gains	29,560,000	29,721,000
Gross unrealized losses	1,414,000	236,000
Total available-for-sale investment securities	713,232,000	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	156
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	157
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	109,974,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	561,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	110,535,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	1,413,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	1,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	1,414,000
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	27,822,000	35,576,000
Gross unrealized gains	1,669,000	2,452,000
Gross unrealized losses	0	0
Estimated fair value	29,491,000	38,028,000
Available-for-sale portfolio [Abstract]
Amortized cost	277,971,000	310,541,000
Gross unrealized gains	20,364,000	20,840,000
Gross unrealized losses	21,000	2,000
Total available-for-sale investment securities	298,314,000	331,379,000
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	1
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	4,826,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	23,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	4,849,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	21,000
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	21,000
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	64,688,000	68,115,000
Gross unrealized gains	0	0
Gross unrealized losses	15,902,000	24,269,000
Total available-for-sale investment securities	48,786,000	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	48,786,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	48,786,000
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	15,902,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	15,902,000
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	2,935,000	0
Gross unrealized gains	3,000	0
Gross unrealized losses	0	0
Estimated fair value	2,938,000	0
Available-for-sale portfolio [Abstract]
Amortized cost	14,995,000	21,495,000
Gross unrealized gains	1,236,000	1,360,000
Gross unrealized losses	0	0
Total available-for-sale investment securities	16,231,000	22,855,000
Government Agency Collateralized Mortgage Obligations [Member]
Available-for-sale portfolio [Abstract]
Amortized cost	38,713,000	45,481,000
Gross unrealized gains	1,258,000	1,572,000
Gross unrealized losses	61,000	110,000
Total available-for-sale investment securities	39,910,000	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	9
Held-to-maturity securities in unrealized loss positions, number of positions	11
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	432,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	4,562,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	4,994,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	2,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	59,000
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		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	381,000	380,000
Gross unrealized gains	80,000	92,000
Gross unrealized losses	79,000	82,000
Total available-for-sale investment securities	382,000	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	2
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	5
Held-to-maturity securities, Debt maturities, Fair value [Abstract]
Held-to-maturity securities, Unrealized Loss Position, Less than 12 months, Fair value	137,000
Held-to-maturity securities, Unrealized Loss Position, 12 Months or longer, Fair value	13,000
Held-to-maturity securities, Unrealized Loss Position, Fair Value	150,000
Held-to-maturity securities, Debt maturities, Gross unrealized losses [Abstract]
Held-to-maturity Securities, Unrealized Loss Position, Less than 12 Months, Gross unrealized losses	76,000
Held-to-maturity Securities, Unrealized Loss Position, 12 Months or Longer, Gross unrealized losses	3,000
Held-to-maturity Securities, Unrealized Loss Position, Gross unrealized losses	79,000
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	57,452,000	38,343,000
Other investment securities , estimated fair value	57,452,000	38,343,000
Other Equity Securities [Member]
Held-to-maturity portfolio [Abstract]
Amortized cost	27,000	36,000
Gross unrealized gains	0	0
Gross unrealized losses	0	0
Estimated fair value	27,000	36,000
Other Securities [Abstract]
Other investment securities, cost	5,121,000	5,108,000
Other investment securities , estimated fair value	$ 5,121,000	$ 5,108,000