INTEREST-BEARING DEPOSITS AND SECURITIES (Schedule of Investments) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Open Option Contracts Written [Line Items]
Interest-bearing deposits included in cash and due from banks	$ 143,251	$ 69,758	$ 234,824
Interest-bearing deposits and marketable securities	801,466	729,089	820,573
U.S. Government and agency obligations [Member]
Open Option Contracts Written [Line Items]
Marketable securities	159,885	341,606	292,012
Total securities [Member]
Open Option Contracts Written [Line Items]
Marketable securities	621,177	621,960	548,378
Total municipal bonds [Member]
Open Option Contracts Written [Line Items]
Marketable securities	132,913	107,460	107,652
Taxable municipal bonds [Member]
Open Option Contracts Written [Line Items]
Marketable securities	26,742	18,497	15,220
Tax exempt municipal bonds [Member]
Open Option Contracts Written [Line Items]
Marketable securities	106,171	88,963	92,432
Corporate bonds [Member]
Open Option Contracts Written [Line Items]
Marketable securities	40,505	42,565	52,238
Total mortgage-backed or related securities [Member]
Open Option Contracts Written [Line Items]
Marketable securities	255,072	129,927	95,931
Fannie Mae (FNMA) [Member]
Open Option Contracts Written [Line Items]
Marketable securities	158,334	66,519	47,177
Freddie Mac (FHLMC) [Member]
Open Option Contracts Written [Line Items]
Marketable securities	65,661	42,001	25,350
Ginnie Mae (GNMA) [Member]
Open Option Contracts Written [Line Items]
Marketable securities	29,665	19,572	20,815
Private issuer [Member]
Open Option Contracts Written [Line Items]
Marketable securities	1,412	1,835	2,589
Student Loan Marketing Assocation (SLMA) [Member]
Open Option Contracts Written [Line Items]
Marketable securities	32,752	0	0
Equity securities (excludes FHLB stock) [Member]
Open Option Contracts Written [Line Items]
Marketable securities	50	402	545
FHLB stock [Member]
Open Option Contracts Written [Line Items]
Marketable securities	$ 37,038	$ 37,371	$ 37,371