SECURITIES AVAILABLE FOR SALE - UNREALIZED LOSSES (Details) $ in Thousands	Dec. 31, 2017 USD ($) item	Dec. 31, 2016 USD ($)
Securities with unrealized losses
Less than 12 Months, Fair Value	$ 147,911	$ 175,838
Less than 12 Months, Unrealized Loss	(1,475)	(2,953)
12 Months or More, Fair Value	77,592	13,652
12 Months or More, Unrealized Loss	(2,057)	(739)
Total, Fair Value	225,503	189,490
Total, Unrealized Loss	(3,532)	(3,692)
Trading Assets
Trading Assets	0	5,592
U.S. treasury notes
Securities with unrealized losses
Less than 12 Months, Fair Value	4,024
Less than 12 Months, Unrealized Loss	(22)
Total, Fair Value	4,024
Total, Unrealized Loss	$ (22)
Number of securities having unrealized losses | item	1
Amortized cost (as a percent)	0.60%
U.S. government agencies
Securities with unrealized losses
Less than 12 Months, Fair Value	$ 18,405	28,202
Less than 12 Months, Unrealized Loss	(130)	(299)
12 Months or More, Fair Value	12,692
12 Months or More, Unrealized Loss	(228)
Total, Fair Value	31,097	28,202
Total, Unrealized Loss	$ (358)	(299)
Number of securities having unrealized losses | item	13
Amortized cost (as a percent)	1.10%
States and political subdivisions
Securities with unrealized losses
Less than 12 Months, Fair Value	$ 15,442	27,834
Less than 12 Months, Unrealized Loss	(97)	(716)
12 Months or More, Fair Value	2,769
12 Months or More, Unrealized Loss	(36)
Total, Fair Value	18,211	27,834
Total, Unrealized Loss	$ (133)	(716)
Number of securities having unrealized losses | item	23
Amortized cost (as a percent)	0.70%
Mortgage-backed - residential
Securities with unrealized losses
Less than 12 Months, Fair Value	$ 70,646	88,167
Less than 12 Months, Unrealized Loss	(817)	(1,364)
12 Months or More, Fair Value	54,760	13,652
12 Months or More, Unrealized Loss	(1,513)	(739)
Total, Fair Value	125,406	101,819
Total, Unrealized Loss	$ (2,330)	(2,103)
Number of securities having unrealized losses | item	64
Amortized cost (as a percent)	1.80%
Mortgage-backed - commercial
Securities with unrealized losses
Less than 12 Months, Fair Value	$ 39,394	31,635
Less than 12 Months, Unrealized Loss	(409)	(574)
12 Months or More, Fair Value	7,371
12 Months or More, Unrealized Loss	(280)
Total, Fair Value	46,765	31,635
Total, Unrealized Loss	$ (689)	$ (574)
Number of securities having unrealized losses | item	18
Amortized cost (as a percent)	1.50%