Federal Taxes on Income - Reconciliation of Tax Provision (Benefit) (Details) - USD ($) $ in Thousands	3 Months Ended														6 Months Ended		12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	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, 2015	Sep. 30, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Jun. 30, 2017	Jun. 30, 2016
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income taxes computed at statutory rates															$ 1,258		$ 1,823	$ 2,305	$ 1,853
Tax credits															(157)		0	(78)	0
Tax-exempt income															(138)		(84)	(320)	(358)
Bank-owned life insurance income															(106)		(125)	(499)	(39)
Deferred tax asset valuation allowance															52		(1)	0	0
Adjustment of deferred tax assets and liabilities for enacted change in tax laws															1,092		0	0	0
Other, net															41		(38)	254	1
Total provision (benefit) for income taxes	$ 441	$ 443	$ 345	$ 346	$ 1,461	$ 581	$ 380	$ 429	$ 519	$ 334	$ 500	$ 298	$ 242	$ 417	$ 2,042	$ 853	$ 1,575	$ 1,662	$ 1,457