6. Loans and Allowance for Loan Losses: Financing Receivable, Allowance for Credit Loss (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Period-end amount allocated to: Total	$ 202,353		$ 202,353		$ 179,949
Loans and Leases Receivable, Net of Deferred Income	22,075,761		22,075,761		25,725,700
Total
Beginning balance	180,000	$ 252,000	180,000	$ 300,000
Provision for loan losses	20,000	(15,000)	45,000	(91,000)
Charge-offs	(1,000)	(1,000)	(36,000)	(4,000)
Recoveries	3,000	3,000	13,000	34,000
Net charge-offs	2,000	2,000	(23,000)	30,000
Ending balance	202,000	239,000	202,000	239,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	76,000		76,000		0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	126,000		126,000		180,000
Period-end amount allocated to: Total	202,000		202,000		180,000
Loans, ending balance: Loans individually evaluated for impairment	1,511,000		1,511,000		1,277,000
Loans, ending balance: Loans collectively evaluated for impairment	20,564,000		20,564,000		24,448,000
Loans and Leases Receivable, Net of Deferred Income	22,075,000		22,075,000		25,725,000
Commercial And Industrial
Beginning balance	3,000	74,000	7,000	68,000
Provision for loan losses	80,000	(65,000)	84,000	(61,000)
Charge-offs	0	0	(10,000)	0
Recoveries	1,000	1,000	3,000	3,000
Net charge-offs	1,000	1,000	(7,000)	3,000
Ending balance	84,000	10,000	84,000	10,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	76,000		76,000		0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	8,000		8,000		7,000
Loans, ending balance: Loans individually evaluated for impairment	152,000		152,000		76,000
Loans, ending balance: Loans collectively evaluated for impairment	1,638,000		1,638,000		1,722,000
Commercial And Industrial | Thousand
Period-end amount allocated to: Total	84,000		84,000		7,000
Loans and Leases Receivable, Net of Deferred Income	1,790,000		1,790,000		1,798,000
Commercial Real Estate Portfolio Segment
Beginning balance	150,000	170,000	155,000	179,000
Provision for loan losses	(37,000)	18,000	(26,000)	(16,000)
Charge-offs	0	0	(18,000)	0
Recoveries	1,000	2,000	3,000	27,000
Net charge-offs	1,000	2,000	(15,000)	27,000
Ending balance	114,000	190,000	114,000	190,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0		0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	114,000		114,000		155,000
Loans, ending balance: Loans individually evaluated for impairment	1,359,000		1,359,000		1,201,000
Loans, ending balance: Loans collectively evaluated for impairment	16,966,000		16,966,000		20,188,000
Commercial Real Estate Portfolio Segment | Thousand
Period-end amount allocated to: Total	114,000		114,000		155,000
Loans and Leases Receivable, Net of Deferred Income	18,325,000		18,325,000		21,389,000
Consumer Real Estate
Beginning balance	4,000	8,000	10,000	10,000
Provision for loan losses	0	0	(6,000)	(3,000)
Charge-offs	0	0	0	0
Recoveries	0	0	0	1,000
Net charge-offs	0	0	0	1,000
Ending balance	4,000	8,000	4,000	8,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0		0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	4,000		4,000		10,000
Loans, ending balance: Loans individually evaluated for impairment	0		0		0
Loans, ending balance: Loans collectively evaluated for impairment	1,252,000		1,252,000		1,729,000
Consumer Real Estate | Thousand
Period-end amount allocated to: Total	4,000		4,000		10,000
Loans and Leases Receivable, Net of Deferred Income	1,252,000		1,252,000		1,729,000
Consumer And Other Loans
Beginning balance	8,000	10,000	8,000	11,000
Provision for loan losses	(8,000)	0	(7,000)	(1,000)
Charge-offs	(1,000)	(1,000)	(8,000)	(4,000)
Recoveries	1,000	0	7,000	3,000
Net charge-offs	0	(1,000)	(1,000)	(1,000)
Ending balance	0	9,000	0	9,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0		0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	0		0		8,000
Loans, ending balance: Loans individually evaluated for impairment	0		0		0
Loans, ending balance: Loans collectively evaluated for impairment	708,000		708,000		809,000
Consumer And Other Loans | Thousand
Period-end amount allocated to: Total	0		0		8,000
Loans and Leases Receivable, Net of Deferred Income	708,000		708,000		809,000
Unallocated Financing Receivables
Beginning balance	15,000	10,000	0	32,000
Provision for loan losses	(15,000)	32,000	0	(10,000)
Charge-offs	0	0	0	0
Recoveries	0	0		0
Net charge-offs	0	0	0	0
Ending balance	0	$ 22,000	0	$ 22,000
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment	0		0		0
Financing Receivable, Allowance for Credit Losses, Collectively Evaluated for Impairment	0		0		0
Loans, ending balance: Loans individually evaluated for impairment	0		0		0
Loans, ending balance: Loans collectively evaluated for impairment	0		0		0
Unallocated Financing Receivables | Thousand
Period-end amount allocated to: Total	0		0		0
Loans and Leases Receivable, Net of Deferred Income	$ 0		$ 0		$ 0