SECURITIES (Details) (USD $)	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Investments, Debt and Equity 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	1,147,157,000	1,613,019,000
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	45,000
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	2,506,757,000		1,074,350,000
Gross Unrealized Gains	57,124,000		25,321,000
Gross Unrealized Losses	3,057,000		3,609,000
Estimated Fair Value	2,560,824,000	962,692,000	1,096,062,000
Gross gains recognized on available-for-sale securities	10,300,000	2,000,000
Gross losses recognized on available-for-sale securities	260,000	1,300,000
Equity securities, considered maturity (in years)	10Y
Available-for-sale securities, amortized cost, by contractual maturity [Abstract]
Maturing in one year or less	330,416,000
Maturing after one year through five years	1,443,567,000
Maturing after five years through ten years	266,506,000
Maturing after ten years	466,268,000
Total	2,506,757,000
Available-for-sale securities, estimated fair value, by contractual maturity [Abstract]
Maturing in one year or less	337,666,000
Maturing after one year through five years	1,468,183,000
Maturing after five years through ten years	273,532,000
Maturing after ten years	481,443,000
Total	2,560,824,000	962,692,000	1,096,062,000
Available-for-sale securities, weighted average yield, by contractual maturity [Abstract]
Maturing in one year or less (in hundredths)	5.09%
Maturing after one year through five years (in hundredths)	2.00%
Maturing after five years through ten years (in hundredths)	3.48%
Maturing after ten years (in hundredths)	5.61%
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value	258,332,000		93,289,000
Less Than 12 Months Unrealized Losses	(2,854,000)		645,000
12 Months or Longer Fair Value	5,211,000		5,062,000
12 Months or Longer Unrealized Losses	(203,000)		272,000
Total Fair Value Available-for-sale Securities	263,543,000		98,351,000
Total Unrealized Losses Available-for-sale Securities	(3,057,000)		917,000
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	1,565,900,000		416,005,000
Gross Unrealized Gains	33,475,000		17,153,000
Gross Unrealized Losses	144,000		0
Estimated Fair Value	1,599,231,000		433,158,000
Available-for-sale securities, estimated fair value, by contractual maturity [Abstract]
Total	1,599,231,000		433,158,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value	79,782,000		48,881,000
Less Than 12 Months Unrealized Losses	(144,000)		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	79,782,000		48,881,000
Total Unrealized Losses Available-for-sale Securities	(144,000)		207,000
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	472,860,000		110,946,000
Gross Unrealized Gains	14,727,000		965,000
Gross Unrealized Losses	934,000		1,746,000
Estimated Fair Value	486,653,000		110,165,000
Available-for-sale securities, estimated fair value, by contractual maturity [Abstract]
Total	486,653,000		110,165,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value	35,576,000		36,704,000
Less Than 12 Months Unrealized Losses	(814,000)		297,000
12 Months or Longer Fair Value	1,248,000		2,459,000
12 Months or Longer Unrealized Losses	(120,000)		205,000
Total Fair Value Available-for-sale Securities	36,824,000		39,163,000
Total Unrealized Losses Available-for-sale Securities	(934,000)		502,000
Government Agency Issued Residential Mortgage-Backed Securities [Member]
Available-for-sale securities [Abstract]
Amortized Cost	425,416,000		498,874,000
Gross Unrealized Gains	6,847,000		5,954,000
Gross Unrealized Losses	1,861,000		1,599,000
Estimated Fair Value	430,402,000		503,229,000
Available-for-sale securities, estimated fair value, by contractual maturity [Abstract]
Total	430,402,000		503,229,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value	140,877,000		6,320,000
Less Than 12 Months Unrealized Losses	(1,861,000)		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	140,877,000		6,320,000
Total Unrealized Losses Available-for-sale Securities	(1,861,000)		122,000
Government Agency Issued Commercial Mortgage-Backed Securities [Member]
Available-for-sale securities [Abstract]
Amortized Cost	30,420,000		29,582,000
Gross Unrealized Gains	1,325,000		676,000
Gross Unrealized Losses	118,000		264,000
Estimated Fair Value	31,627,000		29,994,000
Available-for-sale securities, estimated fair value, by contractual maturity [Abstract]
Total	31,627,000		29,994,000
Available-for-sale securities with continuous unrealized loss positions [Abstract]
Less Than 12 Months Fair Value	2,097,000		1,384,000
Less Than 12 Months Unrealized Losses	(35,000)		19,000
12 Months or Longer Fair Value	3,963,000		2,598,000
12 Months or Longer Unrealized Losses	(83,000)		66,000
Total Fair Value Available-for-sale Securities	6,060,000		3,982,000
Total Unrealized Losses Available-for-sale Securities	(118,000)		85,000
Other [Member]
Available-for-sale securities [Abstract]
Amortized Cost	12,161,000		18,943,000
Gross Unrealized Gains	750,000		573,000
Gross Unrealized Losses	0		0
Estimated Fair Value	12,911,000		19,516,000
Available-for-sale securities, estimated fair value, by contractual maturity [Abstract]
Total	12,911,000		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
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