Mortgage Loans and Interest Rate Swaps (Details) $ in Thousands			9 Months Ended
	May 07, 2021 USD ($)	Mar. 17, 2021	Sep. 30, 2021 USD ($) derivative item	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Long-Term Debt
Loans, prior to debt issuance costs			$ 14,662
Mortgage loans, net of debt issuance costs			166,457		$ 160,655
Mortgage loan net on asset held for sale			4,816
Total mortgage loans, net of debt issuance costs			$ 152,236		160,655
Interest rate swap agreement
Debt disclosures
Number of interest rate swap derivatives | derivative			13
Notional amount of interest rate swap agreement			$ 95,679		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			$ 3,587	$ (6,607)
Loss expected to be reclassified over next twelve months from accumulated other comprehensive loss to interest expense			(1,962)
Net derivative liability fair value			5,179
Interest expense			1,504	$ 1,058
Interest rate swap agreement | Other assets
Debt disclosures
Derivative asset fair value			156
Interest rate swap agreement | Other liabilities
Debt disclosures
Derivative liability fair value			$ 5,335
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			$ 158,942		162,768
Debt issuance costs, net			(1,890)		(2,113)
Mortgage loans, net of debt issuance costs			$ 157,052		$ 160,655
Weighted average interest rate			3.98%		4.18%
Construction loan
Long-Term Debt
Debt issuance costs, net			$ (441)
Mortgage loans, net of debt issuance costs			14,221
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			$ 3,979		$ 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			$ 17,982		$ 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			$ 12,394		$ 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			$ 23,345		$ 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			$ 9,545		$ 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			$ 11,236		$ 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			$ 17,262		$ 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			$ 4,843		$ 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			$ 3,393		$ 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			$ 6,224		$ 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			$ 14,387		$ 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			$ 4,948		$ 5,046
Interest rate (as a percent)			3.50%
4.33%, due August 1, 2030
Long-Term Debt
Loans, prior to debt issuance costs			$ 15,963		$ 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			$ 13,441		$ 13,688
Interest rate (as a percent)			4.51%		4.51%
JPM Construction Loan Two Thousand Twenty One [Member]
Debt disclosures
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%
Nonrecourse Variable Rate Mortgage On Assets Held For Sale Due On July 1 2029 [Member]
Long-Term Debt
Mortgage loan net on asset held for sale			$ (4,816)
Interest rate (as a percent)			5.09%		5.09%