INCOME TAXES: (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Federal income taxes computed at the statutory rate	$ 13,763	$ 12,810	$ 12,122
Add (deduct) tax effect of:
Tax exempt income	(2,643)	(2,551)	(2,495)
ESOP dividend deduction	(98)	(115)	(103)
State tax, net of federal benefit	2,068	2,034	1,846
General business tax credits	(1,648)	(148)	(148)
Other, net	250	97	(77)
TOTAL	$ 11,692	$ 12,127	$ 11,145