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
Jun. 30, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost $ 948,639 $ 947,597
Gross Unrealized Gains 15,513 10,480
Gross Unrealized (Losses) (3,615) (11,313)
Estimated Fair Value 960,537 946,764
Obligations of States and Political Subdivisions    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 270,206 274,007
Gross Unrealized Gains 9,087 4,962
Gross Unrealized (Losses) (753) (3,079)
Estimated Fair Value 278,540 275,890
Corporate and Other Bonds    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 116,318 123,674
Gross Unrealized Gains 1,009 892
Gross Unrealized (Losses) (909) (2,786)
Estimated Fair Value 116,418 121,780
Mortgage-Backed Securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 548,229 536,031
Gross Unrealized Gains 5,417 4,626
Gross Unrealized (Losses) (1,895) (5,371)
Estimated Fair Value 551,751 535,286
Other Securities    
Schedule of Available-for-sale Securities [Line Items]    
Amortized Cost 13,886 13,885
Gross Unrealized Gains 0 0
Gross Unrealized (Losses) (58) (77)
Estimated Fair Value $ 13,828 $ 13,808