Investments: Narrative (Details)	1 Months Ended	3 Months Ended		9 Months Ended
	Jan. 31, 2020 USD ($)	Sep. 30, 2023 USD ($) securities	Sep. 30, 2022 USD ($)	Sep. 30, 2023 USD ($) securities	Sep. 30, 2022 USD ($)	Dec. 31, 2022 USD ($) securities
Debt Securities, Available-for-sale [Line Items]
Securities in unrealized loss position | securities		131		131		123
Securities in unrealized loss position for 12 months or more | securities		114		114		62
Investments pledged as collateral for FHLB advances		50.00%		50.00%
Investments pledged as collateral for public deposits		$ 26,000,000		$ 26,000,000		$ 21,000,000
Gain on sale of investments available-for-sale			$ 0		$ 0
Proceeds from calls and maturities of investments available-for-sale				0	3,781,000
Payments to acquire marketable securities	$ 2,400,000			0	89,687,000
Investments held-to-maturity		2,450,000		2,450,000		2,444,000
Principal repayments on investments available-for-sale		0	$ 399,000	0	$ 3,800,000
Fair value of securities		202,243,000		202,243,000		207,998,000
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Fair value of securities		$ 28,314,000		$ 28,314,000		$ 30,480,000