ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS), Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended		12 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				$ 598,567	$ 565,868	$ 565,868
Other comprehensive income (loss) before reclassifications				57	(177)
Amounts reclassified from accumulated other comprehensive loss				(873)	469
Other comprehensive income (loss), net of tax		$ (541)	$ (133)	(816)	292
Reclassification of tax effects on other comprehensive income	[1]			32
Balance		615,532	580,448	$ 615,532	580,448	$ 598,567
Corporate income tax rate				21.00%		35.00%
ASU 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				$ 598,567
Reclassification of unrealized gains and losses on marketable equity securities						$ 0
Balance						598,567
Accumulated Other Comprehensive Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				(3,641)	(5,939)	(5,939)
Balance		(4,578)	(5,647)	(4,578)	(5,647)	(3,641)
Accumulated Other Comprehensive Gain (Loss) [Member] | ASU 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				(3,794)
Reclassification of unrealized gains and losses on marketable equity securities	[2]					(153)
Balance						(3,794)
Securities Held-to-Maturity and Transferred Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				0	(713)	(713)
Other comprehensive income (loss) before reclassifications				0	36
Amounts reclassified from accumulated other comprehensive loss				0	0
Other comprehensive income (loss), net of tax				0	36
Reclassification of tax effects on other comprehensive income	[1]			0
Balance		0	(677)	0	(677)	0
Securities Held-to-Maturity and Transferred Securities [Member] | ASU 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				0
Reclassification of unrealized gains and losses on marketable equity securities	[2]					0
Balance						0
Securities Available-for-Sale [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				285	(92)	(92)
Other comprehensive income (loss) before reclassifications				(1,931)	125
Amounts reclassified from accumulated other comprehensive loss				(922)	0
Other comprehensive income (loss), net of tax				(2,853)	125
Reclassification of tax effects on other comprehensive income	[1]			0
Balance		(2,721)	33	(2,721)	33	285
Securities Available-for-Sale [Member] | ASU 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				132
Reclassification of unrealized gains and losses on marketable equity securities	[2]					(153)
Balance						132
Defined Benefit Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				(6,633)	(6,910)	(6,910)
Other comprehensive income (loss) before reclassifications				80	(7)
Amounts reclassified from accumulated other comprehensive loss				217	372
Other comprehensive income (loss), net of tax				297	365
Reclassification of tax effects on other comprehensive income	[1]			32
Balance		(6,304)	(6,545)	(6,304)	(6,545)	(6,633)
Defined Benefit Plans [Member] | ASU 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				(6,633)
Reclassification of unrealized gains and losses on marketable equity securities	[2]					0
Balance						(6,633)
Derivative Asset [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				2,707	1,776	1,776
Other comprehensive income (loss) before reclassifications				1,908	(331)
Amounts reclassified from accumulated other comprehensive loss				(168)	97
Other comprehensive income (loss), net of tax				1,740	(234)
Reclassification of tax effects on other comprehensive income	[1]			0
Balance		$ 4,447	$ 1,542	4,447	$ 1,542	2,707
Derivative Asset [Member] | ASU 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance				$ 2,707
Reclassification of unrealized gains and losses on marketable equity securities	[2]					0
Balance						$ 2,707

[1] Represents the impact of adopting ASU 2018-02 allowing the reclassification of certain stranded income tax effects in accumulated other comprehensive income resulting from the Tax Cuts and Jobs Act of 2017 (the "Tax Act") from accumulated other comprehensive income to retained earnings in each period in which the effect of the change in the U.S. federal corporate income tax rate in the Tax Act (or portion thereof) is recorded. The amount of the reclassification is an adjustment for the difference between the historical corporate income tax rate (35%) and the newly enacted 21% corporate income tax rate.

[2] Represents the impact of adopting ASU 2016-01 allowing the reclassification of unrealized gains and losses on available-for-sale equity securities from accumulated other comprehensive income to retained earnings.