Quarterly report pursuant to Section 13 or 15(d)

SECURITIES (Schedule of Gross Unrealized Losses and Fair Value of Investments) (Details)

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SECURITIES (Schedule of Gross Unrealized Losses and Fair Value of Investments) (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Schedule of gross unrealized losses and fair value of investments [Line Items]    
Less than 12 months, Fair Value $ 703,282 $ 335,205
Less than 12 months, Unrealized Losses (13,533) (3,498)
More than 12 Months, Fair Value 193,221 197,640
More than 12 months, Unrealized Losses (6,477) (4,188)
Total, Fair Value 896,503 532,845
Total, Unrealized Losses (20,010) (7,686)
Obligations of States and Political Subdivisions    
Schedule of gross unrealized losses and fair value of investments [Line Items]    
Less than 12 months, Fair Value 150,366 25,790
Less than 12 months, Unrealized Losses (3,288) (132)
More than 12 Months, Fair Value 16,413 16,934
More than 12 months, Unrealized Losses (891) (432)
Total, Fair Value 166,779 42,724
Total, Unrealized Losses (4,179) (564)
Mortgage-Backed Securities    
Schedule of gross unrealized losses and fair value of investments [Line Items]    
Less than 12 months, Fair Value 531,141 298,439
Less than 12 months, Unrealized Losses (10,089) (3,267)
More than 12 Months, Fair Value 139,217 136,298
More than 12 months, Unrealized Losses (4,672) (2,902)
Total, Fair Value 670,358 434,737
Total, Unrealized Losses (14,761) (6,169)
Corporate Bonds and Other Securities    
Schedule of gross unrealized losses and fair value of investments [Line Items]    
Less than 12 months, Fair Value 21,775 10,976
Less than 12 months, Unrealized Losses (156) (99)
More than 12 Months, Fair Value 37,591 44,408
More than 12 months, Unrealized Losses (914) (854)
Total, Fair Value 59,366 55,384
Total, Unrealized Losses $ (1,070) $ (953)