INCOME TAXES: (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal:
Currently payable	$ 8,303	$ 15,514	$ 9,890
Deferred	3,756	1,326	(774)
Federal tax reform	6,282
Federal income tax expense (benefit), continuing operations	18,341	16,840	9,116
State:
Currently payable	1,818	2,857	1,426
Deferred	463	186	(150)
State and local income tax expense (benefit), continuing operations	2,281	3,043	1,276
TOTAL	$ 20,622	$ 19,883	$ 10,392