INVESTMENT SECURITIES (Details 5) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2013 item		Dec. 31, 2012 item
Schedule of Available-for-sale Securities
Fair value of available for sale securities		$ 2,588,993,000		$ 2,607,029,000
Continuous unrealized loss position 12 months or more, fair value		118,665,000		195,271,000
Number of securities in a continuous unrealized loss position for more than twelve months		10		13
Number of individual securities with a continuous unrealized loss position less than 12 months		117		77
Gross unrealized losses in loss position twelve months or more		(11,402,000)		(19,739,000)
US Government Agencies and Government Sponsored Enterprise Debt Securities
Schedule of Available-for-sale Securities
Number of individual securities with a continuous unrealized loss position less than 12 months		1		1
Residential mortgage-backed securities
Schedule of Available-for-sale Securities
Number of individual securities with a continuous unrealized loss position less than 12 months		31		26
Corporate debt securities | Investment grade
Schedule of Available-for-sale Securities
Fair value of available for sale securities		453,323,000		411,983,000
Continuous unrealized loss position 12 months or more, fair value		105,279,000		182,697,000
Total investment securities available-for-sale portfolio (as a percent)		18.00%		16.00%
Number of securities in a continuous unrealized loss position for more than twelve months		5		8
Number of individual securities with a continuous unrealized loss position less than 12 months		4		11
Gross unrealized losses in loss position twelve months or more		(4,721,000)		(12,181,000)
Corporate debt securities | Non-investment grade
Schedule of Available-for-sale Securities
Fair value of available for sale securities		18,000,000	[1]	17,417,000	[1]
Continuous unrealized loss position 12 months or more, fair value		13,386,000		12,574,000
Number of individual securities with a continuous unrealized loss position less than 12 months		1
Percentage of total amortized cost basis of these securities		33.00%
Gross unrealized losses in loss position twelve months or more		(6,681,000)		(7,558,000)
Gross unrealized losses, trust preferred securities, portion representing impairment loss on securities not other-than-temporarily-impaired	5,600,000
Gross unrealized losses, trust preferred securities, portion representing non-credit impairment loss on securities other-than-temporarily-impaired	5,100,000
Trust Preferred Securities | Non-investment grade
Schedule of Available-for-sale Securities
Continuous unrealized loss position 12 months or more, fair value		13,400,000		12,600,000
Total investment securities available-for-sale portfolio (as a percent)		1.00%
Number of securities in a continuous unrealized loss position for more than twelve months		5		5
Impairment loss relating to additional increases to the amount related to the credit loss for which an other-than-temporary impairment was previously recognized	99,000
Municipal securities
Schedule of Available-for-sale Securities
Fair value of available for sale securities		206,758,000		167,093,000
Total investment securities available-for-sale portfolio (as a percent)		8.00%		6.00%
Number of individual securities with a continuous unrealized loss position less than 12 months		68		29
Other securities
Schedule of Available-for-sale Securities
Fair value of available for sale securities		10,793,000		10,170,000
U.S. Treasury securities
Schedule of Available-for-sale Securities
Fair value of available for sale securities		470,764,000		460,677,000
Number of individual securities with a continuous unrealized loss position less than 12 months		5		9
Other commercial mortgage-backed securities: | Investment grade
Schedule of Available-for-sale Securities
Fair value of available for sale securities		51,359,000		17,084,000
U.S. Government agency and U.S. Government sponsored enterprise mortgage-backed securities - Commercial mortgage-backed securities
Schedule of Available-for-sale Securities
Fair value of available for sale securities		$ 145,044,000		$ 180,665,000
Number of individual securities with a continuous unrealized loss position less than 12 months		7		1

[1] For the three months ended March 31, 2013, the Company did not record any OTTI. The Company recorded $99 thousand, on a pre-tax basis, of the credit portion of OTTI through earnings and $5.1 million of the non-credit portion of OTTI for pooled trust preferred securities in other comprehensive income for the year ended December 31, 2012.