ALLOWANCE FOR LOAN LOSSES: (Details 1) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Ending Balance Attributable to Loans
Individually evaluated for impairment	$ 625	$ 331
Collectively evaluated for impairment	19,284	18,442
BALANCE AT END OF YEAR	19,909	18,773	$ 19,946	$ 18,839
Loans
Individually evaluated for impairment	10,082	8,600
Collectively evaluated for impairment	1,901,080	1,831,594
BALANCE AT END OF YEAR	1,913,022	1,845,040
Commercial
Ending Balance Attributable to Loans
Individually evaluated for impairment	619	242
Collectively evaluated for impairment	9,662	9,489
BALANCE AT END OF YEAR	10,281	9,731	11,482	10,915
Loans
Individually evaluated for impairment	9,619	8,051
Collectively evaluated for impairment	1,134,701	1,101,269
BALANCE AT END OF YEAR	1,146,180	1,112,735
Residential
Ending Balance Attributable to Loans
Individually evaluated for impairment	6	89
Collectively evaluated for impairment	1,449	1,464
BALANCE AT END OF YEAR	1,455	1,553	1,834	1,374
Loans
Individually evaluated for impairment	463	549
Collectively evaluated for impairment	436,944	423,099
BALANCE AT END OF YEAR	437,407	425,079
Consumer
Ending Balance Attributable to Loans
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	6,709	5,767
BALANCE AT END OF YEAR	6,709	5,767	4,945	4,370
Loans
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	329,435	307,226
BALANCE AT END OF YEAR	329,435	307,226
Unallocated
Ending Balance Attributable to Loans
Individually evaluated for impairment	0	0
Collectively evaluated for impairment	1,464	1,722
BALANCE AT END OF YEAR	1,464	1,722	$ 1,685	$ 2,180
Acquired with deteriorated credit quality
Ending Balance Attributable to Loans
Acquired with deteriorated credit quality	0	0
Loans
Acquired with deteriorated credit quality	1,860	4,846
Acquired with deteriorated credit quality | Commercial
Ending Balance Attributable to Loans
Acquired with deteriorated credit quality	0	0
Loans
Acquired with deteriorated credit quality	1,860	3,415
Acquired with deteriorated credit quality | Residential
Ending Balance Attributable to Loans
Acquired with deteriorated credit quality	0	0
Loans
Acquired with deteriorated credit quality	0	1,431
Acquired with deteriorated credit quality | Consumer
Ending Balance Attributable to Loans
Acquired with deteriorated credit quality	0	0
Loans
Acquired with deteriorated credit quality	0	0
Acquired with deteriorated credit quality | Unallocated
Ending Balance Attributable to Loans
Acquired with deteriorated credit quality	$ 0	$ 0