Other Income (Narrative) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Other Income [Line Items]
Cash proceeds from insurance settlement									$ 534,000	$ 589,000	$ 233,000
Gain on insurance settlement	$ 616,000	$ 34,000	$ 2,000	$ 52,000	$ 279,000	$ 31,000	$ 272,000		652,000	634,000	$ 233,000
Des Moines, Iowa market
Other Income [Line Items]
Cash proceeds from insurance settlement	445,000				290,000		250,000
Gain on insurance settlement	$ 445,000				$ 290,000		$ 250,000			$ 540,000
Bellingham, Washington
Other Income [Line Items]
Proceeds from sale of land and buildings								$ 1,700,000
Gain on sale of land and buildings								1,400,000
Keene, New Hampshire market
Other Income [Line Items]
Cash proceeds from insurance settlement								208,000
Gain on insurance settlement								$ 208,000
Other Nonoperating Income (Expense) [Member]
Other Income [Line Items]
Reimbursements received									$ 116,000