Mortgage Loans and Interest Rate Swaps (Details) $ in Thousands			6 Months Ended
	May 07, 2021 USD ($) ft²	Mar. 17, 2021	Jun. 30, 2021 USD ($) derivative item	Jun. 30, 2020 USD ($)	Aug. 09, 2021 USD ($)	Dec. 31, 2020 USD ($)
Long-Term Debt
Loans, net of debt issuance costs			$ 157,724			$ 160,655
Interest rate swap agreement
Debt disclosures
Number of interest rate swap derivatives | derivative			13
Notional amount of interest rate swap agreement			$ 96,414			97,868
Number of agreements containing credit risk related contingent features | item			0
Recognized net gains (losses) (included in other comprehensive loss), before taxes, on interest rate swap agreements			$ 2,963	$ (7,091)
Loss expected to be reclassified over next twelve months from accumulated other comprehensive loss to interest expense			(1,964)
Net derivative liability fair value			5,803
Interest expense			994	$ 549
Interest rate swap agreement | Other assets
Debt disclosures
Derivative asset fair value			134
Interest rate swap agreement | Other liabilities
Debt disclosures
Derivative liability fair value			$ 5,937
LIBOR | Maximum
Debt disclosures
Variable interest rate margin (as a percent)			1.65%
Nonrecourse mortgage loans
Long-Term Debt
Loans, prior to debt issuance costs			$ 160,228			162,768
Debt issuance costs, net			(1,964)			(2,113)
Loans, net of debt issuance costs			$ 158,264			$ 160,655
Weighted average interest rate			4.18%			4.18%
Construction loan
Long-Term Debt
Debt issuance costs, net			$ (540)
Acquisition Credit Line | LIBOR
Debt disclosures
Variable interest rate margin (as a percent)		2.75%
4.72%, due October 3, 2022
Long-Term Debt
Loans, prior to debt issuance costs			$ 4,007			$ 4,061
Interest rate (as a percent)			4.72%			4.72%
4.39%, due January 2, 2025
Long-Term Debt
Loans, prior to debt issuance costs			$ 18,140			$ 18,453
Interest rate (as a percent)			4.39%			4.39%
4.17%, due May 1, 2026
Long-Term Debt
Loans, prior to debt issuance costs			$ 12,495			$ 12,696
Interest rate (as a percent)			4.17%			4.17%
3.79%, November 17, 2026
Long-Term Debt
Loans, prior to debt issuance costs			$ 23,535			$ 23,911
Interest rate (as a percent)			3.79%			3.79%
4.39%, due August 1, 2027
Long-Term Debt
Loans, prior to debt issuance costs			$ 9,614			$ 9,750
Interest rate (as a percent)			4.39%			4.39%
3.97%, due September 1, 2027
Long-Term Debt
Loans, prior to debt issuance costs			$ 11,298			$ 11,419
Interest rate (as a percent)			3.97%			3.97%
4.57%, due February 1, 2028
Long-Term Debt
Loans, prior to debt issuance costs			$ 17,375			$ 17,601
Interest rate (as a percent)			4.57%			4.57%
5.09%, due July 1, 2029 GCD mortgage loan
Long-Term Debt
Loans, prior to debt issuance costs			$ 4,968			$ 5,214
Interest rate (as a percent)			5.09%			5.09%
5.09%, due July 1, 2029 TD mortgage Loan
Long-Term Debt
Loans, prior to debt issuance costs			$ 3,481			$ 3,653
Interest rate (as a percent)			5.09%			5.09%
3.60%, due January 2, 2030
Long-Term Debt
Loans, prior to debt issuance costs			$ 6,267			$ 6,350
Interest rate (as a percent)			3.60%	3.60%
3.48% due February 1 2030
Long-Term Debt
Loans, prior to debt issuance costs			$ 14,486			$ 14,682
Interest rate (as a percent)			3.48%			3.48%
3.50%, due July 1, 2030
Long-Term Debt
Loans, prior to debt issuance costs			$ 4,981			$ 5,046
Interest rate (as a percent)			3.50%
4.33%, due August 1, 2030
Long-Term Debt
Loans, prior to debt issuance costs			$ 16,057			$ 16,244
Interest rate (as a percent)			4.33%			4.33%
4.51%, due April 1, 2034
Long-Term Debt
Loans, prior to debt issuance costs			$ 13,524			$ 13,688
Interest rate (as a percent)			4.51%			4.51%
JPM Construction Loan Two Thousand Twenty One [Member]
Long-Term Debt
Loans, net of debt issuance costs			$ 0		$ 9,594
Debt disclosures
Area Of Building | ft²	141,000
Term of debt	2 years
Extension term of debt	1 year
JPM Construction Loan Two Thousand Twenty One [Member] | Maximum
Debt disclosures
Loan amount	$ 28,400
Face amount as a percentage of total cost	67.50%
JPM Construction Loan Two Thousand Twenty One [Member] | LIBOR | Completion of Charlotte build to suit and commencement of rental payment
Debt disclosures
Variable interest rate margin (as a percent)	1.40%
JPM Construction Loan Two Thousand Twenty One [Member] | LIBOR | Maximum
Debt disclosures
Variable interest rate margin (as a percent)	1.65%