DEPOSITS AND CUSTOMER REPURCHASE AGREEMENTS (Deposit Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012
Banking and Thrift [Abstract]
Non-interest-bearing accounts	$ 1,051,831	$ 981,240	$ 918,962
Interest-bearing checking	399,343	410,316	379,650
Regular savings accounts	775,260	727,957	689,322
Money market accounts	408,827	408,998	411,262
Total transaction and saving accounts	2,635,261	2,528,511	2,399,196
Certificates, within 1 year	667,444	759,626	818,283
Certificates, after 1 year, but within 3 years	183,411	209,790	205,030
Certificates, after 3 years	49,169	59,877	63,863
Total certificate accounts	900,024	1,029,293	1,087,176
Total deposits	3,535,285	3,557,804	3,486,372
Public fund transaction accounts	70,470	79,955	72,407
Public fund interest-bearing certificates	51,562	60,518	61,628
Total public deposits	122,032	140,473	134,035
Total brokered deposits	$ 4,531	$ 15,702	$ 21,403
Non-interest-bearing accounts, percent of total	29.70%	27.60%	26.30%
Interest-bearing checking, percent of total	11.30%	11.50%	10.90%
Regular savings accounts, percent of total	21.90%	20.50%	19.80%
Money market accounts, percent of total	11.60%	11.50%	11.80%
Total transaction and saving accounts, percent of total	74.50%	71.10%	68.80%
Certificates, within 1 year, percent of total	18.90%	21.30%	23.50%
Certificates, after 1 year, but within 3 years, percent of total	5.20%	5.90%	5.90%
Certificates, after 3 years, percent of total	1.40%	1.70%	1.80%
Total certificate accounts, percent of total	25.50%	28.90%	31.20%
Total deposits, percent of total	100.00%	100.00%	100.00%
Public fund transaction accounts, percent of total	2.00%	2.20%	2.00%
Public fund interest-bearing certificates, percent of total	1.50%	1.70%	1.80%
Total public deposits, percent of total	3.50%	3.90%	3.80%
Total brokered deposits, percent of total	0.10%	0.40%	0.60%