PARENT COMPANY CONDENSED FINANCIAL STATEMENTS: (Details 2) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income	$ 2,616	$ 8,794	$ 8,352	$ 9,369	$ 8,344	$ 8,162	$ 8,232	$ 13,675	$ 29,131	$ 38,413	$ 30,196
Adjustments to reconcile net income to net cash provided by operating activities:
Contribution of shares to ESOP									1,062	1,361	1,294
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchases of treasury stock									(503)	(19,396)	(8,698)
Dividends paid									(30,556)	(12,359)	(12,632)
NET CHANGE IN CASH AND CASH EQUIVALENTS									(905)	(13,683)	10,593
CASH AND DUE FROM BANKS, BEGINNING OF YEAR				75,012				88,695	75,012	88,695	78,102
CASH AND DUE FROM BANKS, END OF YEAR	74,107				75,012				74,107	75,012	88,695
Supplemental disclosures of cash flow information:
Interest									6,337	4,432	4,237
Income Taxes									11,158	18,739	12,869
Parent
CASH FLOWS FROM OPERATING ACTIVITIES:
Net Income									29,131	38,413	30,196
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization									195	200	203
Equity in undistributed earnings									645	(7,670)	(11,503)
Contribution of shares to ESOP									1,062	1,361	1,294
Restricted stock compensation									706	684	684
Increase (decrease) in other liabilities									(247)	(262)	(1,524)
(Increase) decrease in other assets									0	12	188
NET CASH FROM OPERATING ACTIVITIES									31,492	32,738	19,538
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of furniture and fixtures									0	0	(65)
NET CASH FROM INVESTING ACTIVITIES									0	0	(65)
CASH FLOWS FROM FINANCING ACTIVITIES:
Purchases of treasury stock									(503)	(19,396)	(8,698)
Dividends paid									(30,556)	(12,359)	(12,632)
NET CASH FROM FINANCING ACTIVITES									(31,059)	(31,755)	(21,330)
NET CHANGE IN CASH AND CASH EQUIVALENTS									433	983	(1,857)
CASH AND DUE FROM BANKS, BEGINNING OF YEAR				$ 2,765				$ 1,782	2,765	1,782	3,639
CASH AND DUE FROM BANKS, END OF YEAR	$ 3,198				$ 2,765				3,198	2,765	1,782
Supplemental disclosures of cash flow information:
Interest									0	0	0
Income Taxes									$ 11,158	$ 18,739	$ 12,869