Quarterly report pursuant to Section 13 or 15(d)

SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details)

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SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($)
$ in Thousands
Mar. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 948,777 $ 947,597
Gross Unrealized Gains 11,375 10,480
Gross Unrealized (Losses) (7,094) (11,313)
Estimated Fair Value 953,058 946,764
Obligations of States and Political Subdivisions    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 274,003 274,007
Gross Unrealized Gains 5,910 4,962
Gross Unrealized (Losses) (2,064) (3,079)
Estimated Fair Value 277,849 275,890
Corporate and Other Bonds    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 112,432 123,674
Gross Unrealized Gains 775 892
Gross Unrealized (Losses) (1,161) (2,786)
Estimated Fair Value 112,046 121,780
Mortgage-Backed Securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 548,457 536,031
Gross Unrealized Gains 4,690 4,626
Gross Unrealized (Losses) (3,792) (5,371)
Estimated Fair Value 549,355 535,286
Other Securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 13,885 13,885
Gross Unrealized Gains 0 0
Gross Unrealized (Losses) (77) (77)
Estimated Fair Value $ 13,808 $ 13,808