SECURITIES (Textuals) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) security	Dec. 31, 2017 USD ($) security	Dec. 31, 2016 USD ($) security
Trading:
Trading securites, proceeds from sale	$ 0	$ 1,258,000	$ 7,839,000
Trading Securities, Realized Gain (Loss)		(28,000)	530,000
Trading securities, OTTI charges	$ 0	$ 0	$ 0
Trading securities, number of securities in nonaccrual status | security	0	0	0
Trading securities, unrealized holding gain	$ 3,767,000	$ 700,000
Available-for-Sale:
Available-for-sale securities, unrealized loss position, number of securities | security	271	226
Available-for-sale securities, proceeds from sale	$ 214,600,000	$ 522,600,000	$ 369,800,000
Available-for-sale securities, Realized Gain (Loss)	(839,000)	(2,100,000)	311,000
Available-for-sale securities, OTTI charges	$ 0	$ 0	$ 0
Available-for-sale Securities, Number of Securities in Nonaccrual Status | security	0	0	0
Held-to-Maturity:
Held-to-maturity Securities, unrealized loss position, number of securities | security	90	66
Held-to-maturity Securities, proceeds from sale	$ 0	$ 0	$ 0
Held-to-maturity securities, number of securities in nonaccrual status | security	0	0	0
Principal repayments and maturities of securities—held-to-maturity	$ 2,000