SECURITIES (Details) (USD $)	6 Months Ended	9 Months Ended
	Jun. 30, 2011	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
SECURITIES [Abstract]
Held to maturity securities transferred security at carrying value	$ 1,600,000,000
Held to maturity securities transferred security at fair value	1,700,000,000
Held to maturity securities transferred to available for sale securities unrealized gain/(loss)	19,700,000
Held-to-maturity securities [Abstract]
Amortized Cost		0	1,357,888,000	1,613,019,000	[1]
Gross Unrealized Gains				31,368,000
Gross Unrealized Losses				11,696,000
Estimated Fair Value				1,632,691,000
Gross gains recognized on held-to-maturity securities		37,000	52,000
Gross losses recognized on held-to-maturity securities		0	0
Held-to-maturity securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value				20,322,000
Less Than 12 Months Unrealized Losses				(332,000)
12 Months or Longer Fair Value				9,327,000
12 Months or Longer Unrealized Losses				(338,000)
Total Fair Value Held-to-maturity Securities				29,649,000
Total Unrealized Losses Held-to-maturity Securities				(670,000)
Available-for-sale securities [Abstract]
Amortized Cost		2,414,971,000		1,074,350,000
Gross Unrealized Gains		67,504,000		25,321,000
Gross Unrealized Losses		920,000		3,609,000
Estimated Fair Value		2,481,555,000	915,877,000	1,096,062,000	[1]
Gross gains recognized on available-for-sale securities		12,400,000	4,500,000
Gross losses recognized on available-for-sale securities		327,000	1,500,000
Equity securities, considered maturity (in years)		10Y
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value		75,093,000		93,289,000
Less Than 12 Months Unrealized Losses		(690,000)		(645,000)
12 Months or Longer Fair Value		7,510,000		5,062,000
12 Months or Longer Unrealized Losses		(230,000)		(272,000)
Total Fair Value Available-for sale Securities		82,603,000		98,351,000
Total Unrealized Losses Available-for-sale Securities		(920,000)		(917,000)
Available-for-sale securities, amortized cost, by contractual maturity [Abstract]
Maturing in one year or less		300,046,000
Maturing after one year through five years		1,583,632,000
Maturing after five years through ten years		108,732,000
Maturing after ten years		422,561,000
Total		2,414,971,000
Available-for-sale securities, estimated fair value, by contractual maturity, [Abstract]
Maturing in one year or less		305,378,000
Maturing after one year through five years		1,620,065,000
Maturing after five years through ten years		113,051,000
Maturing after ten years		443,061,000
Total		2,481,555,000	915,877,000	1,096,062,000	[1]
Available-for-sale securities, weighted average yield, by contractual maturity [Abstract]
Maturing in one year or less (in hundredths)		4.42%
Maturing after one year through five years (in hundredths)		2.13%
Maturing after five years through ten years (in hundredths)		4.48%
Maturing after ten years (in hundredths)		5.76%
U.S. Government Agencies [Member]
Held-to-maturity securities [Abstract]
Amortized Cost				1,246,649,000
Gross Unrealized Gains				27,082,000
Gross Unrealized Losses				4,320,000
Estimated Fair Value				1,269,411,000
Held-to-maturity securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value				0
Less Than 12 Months Unrealized Losses				0
12 Months or Longer Fair Value				0
12 Months or Longer Unrealized Losses				0
Total Fair Value Held-to-maturity Securities				0
Total Unrealized Losses Held-to-maturity Securities				0
U.S. Government Agencies [Member]
Available-for-sale securities [Abstract]
Amortized Cost		1,461,622,000		416,005,000
Gross Unrealized Gains		35,834,000		17,153,000
Gross Unrealized Losses		0		0
Estimated Fair Value		1,497,456,000		433,158,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value		0		48,881,000
Less Than 12 Months Unrealized Losses		0		(207,000)
12 Months or Longer Fair Value		0		0
12 Months or Longer Unrealized Losses		0		0
Total Fair Value Available-for sale Securities		0		48,881,000
Total Unrealized Losses Available-for-sale Securities		0		(207,000)
Available-for-sale securities, estimated fair value, by contractual maturity, [Abstract]
Total		1,497,456,000		433,158,000
Obligations of States and Political Subdivisions [Member]
Held-to-maturity securities [Abstract]
Amortized Cost				366,370,000
Gross Unrealized Gains				4,286,000
Gross Unrealized Losses				7,376,000
Estimated Fair Value				363,280,000
Held-to-maturity securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value				20,322,000
Less Than 12 Months Unrealized Losses				(332,000)
12 Months or Longer Fair Value				9,327,000
12 Months or Longer Unrealized Losses				(338,000)
Total Fair Value Held-to-maturity Securities				29,649,000
Total Unrealized Losses Held-to-maturity Securities				(670,000)
Obligations of States and Political Subdivisions [Member]
Available-for-sale securities [Abstract]
Amortized Cost		500,280,000		110,946,000
Gross Unrealized Gains		19,753,000		965,000
Gross Unrealized Losses		602,000		1,746,000
Estimated Fair Value		519,431,000		110,165,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value		20,750,000		36,704,000
Less Than 12 Months Unrealized Losses		(453,000)		(297,000)
12 Months or Longer Fair Value		3,563,000		2,459,000
12 Months or Longer Unrealized Losses		(149,000)		(205,000)
Total Fair Value Available-for sale Securities		24,313,000		39,163,000
Total Unrealized Losses Available-for-sale Securities		(602,000)		(502,000)
Available-for-sale securities, estimated fair value, by contractual maturity, [Abstract]
Total		519,431,000		110,165,000
Government Agency Issued Residential Mortgage-Backed Securities [Member]
Available-for-sale securities [Abstract]
Amortized Cost		412,826,000		498,874,000
Gross Unrealized Gains		8,100,000		5,954,000
Gross Unrealized Losses		237,000		1,599,000
Estimated Fair Value		420,689,000		503,229,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value		54,343,000		6,320,000
Less Than 12 Months Unrealized Losses		(237,000)		(122,000)
12 Months or Longer Fair Value		0		0
12 Months or Longer Unrealized Losses		0		0
Total Fair Value Available-for sale Securities		54,343,000		6,320,000
Total Unrealized Losses Available-for-sale Securities		(237,000)		(122,000)
Available-for-sale securities, estimated fair value, by contractual maturity, [Abstract]
Total		420,689,000		503,229,000
Government Agency Issued Commercial Mortgage-Backed Securities [Member]
Available-for-sale securities [Abstract]
Amortized Cost		31,313,000		29,582,000
Gross Unrealized Gains		3,243,000		676,000
Gross Unrealized Losses		81,000		264,000
Estimated Fair Value		34,475,000		29,994,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value		0		1,384,000
Less Than 12 Months Unrealized Losses		0		(19,000)
12 Months or Longer Fair Value		3,947,000		2,598,000
12 Months or Longer Unrealized Losses		(81,000)		(66,000)
Total Fair Value Available-for sale Securities		3,947,000		3,982,000
Total Unrealized Losses Available-for-sale Securities		(81,000)		(85,000)
Available-for-sale securities, estimated fair value, by contractual maturity, [Abstract]
Total		34,475,000		29,994,000
Collateralized Debt Obligations [Member]
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value				0
Less Than 12 Months Unrealized Losses				0
12 Months or Longer Fair Value				5,000
12 Months or Longer Unrealized Losses				(1,000)
Total Fair Value Available-for sale Securities				5,000
Total Unrealized Losses Available-for-sale Securities				(1,000)
Other [Member]
Available-for-sale securities [Abstract]
Amortized Cost		8,930,000		18,943,000
Gross Unrealized Gains		574,000		573,000
Gross Unrealized Losses		0		0
Estimated Fair Value		9,504,000		19,516,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value		0		0
Less Than 12 Months Unrealized Losses		0		0
12 Months or Longer Fair Value		0		0
12 Months or Longer Unrealized Losses		0		0
Total Fair Value Available-for sale Securities		0		0
Total Unrealized Losses Available-for-sale Securities		0		0
Available-for-sale securities, estimated fair value, by contractual maturity, [Abstract]
Total		$ 9,504,000		$ 19,516,000

[1] Derived from audited financial statements.