BORROWED FUNDS - Short-term Borrowings and Repurchase Agreements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Borrowed funds
Remaining maximum borrowing capacity with the FHLB	$ 199,800
FHLB and other borrowings	152,169	$ 90,921
Maximum borrowing capacity with the FHLB	434,000
Short-term Borrowings from FHLB
Short-term Borrowings and Repurchase Agreements
Balance at end of year	149,596	87,733	$ 179,917
Average balance during the year	100,969	137,822	121,425
Maximum month-end balance	$ 220,097	$ 210,600	$ 179,917
Weighted-average rate during the year	1.16%	0.51%	0.34%
Weighted-average rate at December 31	1.61%	0.74%	0.44%
Repurchase Agreements
Short-term Borrowings and Repurchase Agreements
Balance at end of year	$ 22,403	$ 25,160	$ 27,437
Average balance during the year	25,160	27,066	26,884
Maximum month-end balance	$ 25,972	$ 29,561	$ 32,470
Weighted-average rate during the year	0.30%	0.27%	0.31%
Weighted-average rate at December 31	0.34%	0.28%	0.30%
Investment Securities
Short-term Borrowings and Repurchase Agreements
Investment securities held as collateral	$ 23,100	$ 26,000
Subordinated Debt
Short-term Borrowings and Repurchase Agreements
Weighted-average rate during the year	6.69%	6.64%	6.57%