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Mortgage Loan (Details) $ in Thousands							3 Months Ended			9 Months Ended
Mortgage Loan (Details) $ in Thousands	Sep. 13, 2016 USD ($)	Apr. 26, 2016 USD ($) ft² building	Dec. 11, 2015 USD ($) subsidiary	Sep. 01, 2015 USD ($) ft² derivative subsidiary	Jul. 29, 2015 USD ($) ft² building	Dec. 31, 2014 USD ($) ft² derivative	May 31, 2016 USD ($)	Feb. 29, 2016 USD ($)	Nov. 30, 2015 USD ($) ft²	Aug. 31, 2016 USD ($) item	Aug. 31, 2015 USD ($)	Dec. 10, 2015 USD ($)
Long-Term Debt
Mortgage loans									$ 90,436	$ 99,838
Debt disclosures
Proceeds from issuance of debt										18,800	$ 28,891
Ineffectiveness on cash flow hedges										0
Anticipated ineffectiveness on cash flow hedges										0
Net fair values of interest rate swap agreements included in other liabilities									2,766	4,639
Other liabilities caption
Debt disclosures
Net fair values of interest rate swap agreements included in other liabilities										4,639
Nonrecourse variable rate loans, due October 2, 2017
Long-Term Debt
Mortgage loans									6,217	6,081
Nonrecourse variable rate loans, due February 1, 2019
Long-Term Debt
Mortgage loans									10,610	10,389
Nonrecourse variable rate loans, due August 1, 2019
Long-Term Debt
Mortgage loans		$ 7,418							7,501
Debt disclosures
Number of buildings used as collateral \| building		4
Area of collateralized properties (in square feet) \| ft²		240,000
Nonrecourse variable rate loans, due January 27, 2020
Long-Term Debt
Mortgage loans									3,729	3,637
Nonrecourse variable rate loans, due January 2, 2025
Long-Term Debt
Mortgage loans									19,385	20,869
Debt disclosures
Proceeds from issuance of debt						$ 10,891
Term of debt						10 years
Amortization period of debt						25 years
Number of subsidiaries which are party to the mortgage \| subsidiary			2
Debt amount refinanced						$ 8,859
Nonrecourse variable rate loans, due January 2, 2025 \| Location 1
Debt disclosures
Area of collateralized properties (in square feet) \| ft²						303,000
Leased space \| ft²						201,000
Nonrecourse variable rate loans, due January 2, 2025 \| Location 2
Debt disclosures
Area of collateralized properties (in square feet) \| ft²						228,000
Nonrecourse variable rate mortgage, due September 1, 2025
Long-Term Debt
Mortgage loans									11,457	13,809
Debt disclosures
Area of collateralized properties (in square feet) \| ft²				280,000
Term of debt				10 years
Amortization period of debt				25 years
Leased space \| ft²				196,000
Number of subsidiaries which are party to the mortgage \| subsidiary				1
Nonrecourse Variable Rate Mortgage, Refinanced, Due In September 2026 [Member] \| Subsequent events
Debt disclosures
Term of debt	10 years
Amortization period of debt	25 years
Loan amount increase	$ 13,000
Nonrecourse Variable Rate Mortgage Due On 1 May 2026 [Member]
Long-Term Debt
Mortgage loans										14,269
Debt disclosures
New mortgage		$ 14,350
Number of buildings used as collateral \| building		4
Proceeds from issuance of debt		$ 6,932
Term of debt		10 years
Amortization period of debt		25 years
Additional area serving as collateral \| ft²		98,000
Nonrecourse Variable Rate Mortgage Due On 1 May 2026 [Member] \| Location 1
Debt disclosures
Leased space \| ft²		58,000
Nonrecourse Variable Rate Mortgage Due On 1 May 2026 [Member] \| Location 2
Debt disclosures
Leased space \| ft²		40,000
5.09%, due July 1, 2029 GCD mortgage loan
Long-Term Debt
Mortgage loans									$ 7,385	$ 7,099
Interest rate (as a percent)									5.09%	5.09%
5.09%, due July 1, 2029 TD mortgage Loan
Long-Term Debt
Mortgage loans									$ 6,226	$ 5,984
Interest rate (as a percent)									5.09%	5.09%
4.33%, due August 1, 2030 mortgage loan
Long-Term Debt
Mortgage loans									$ 17,926	$ 17,701
Interest rate (as a percent)									4.33%	4.33%
Debt disclosures
New mortgage					$ 18,000
Number of buildings used as collateral \| building					3
Proceeds from issuance of debt					$ 14,875
Term of debt					15 years
Amortization period of debt					30 years
Nonrecourse mortgages: 5.73%, due August 1, 2015
Long-Term Debt
Mortgage loans					$ 17,891
Interest rate (as a percent)					5.73%
Debt disclosures
Number of buildings used as collateral \| building					3
Area of collateralized properties (in square feet) \| ft²					392,000
Interest rate swap agreement
Debt disclosures
Number of agreements containing credit risk related contingent features \| item										0
Recognized net losses (included in other comprehensive loss), before taxes, on interest rate swap agreements										$ 2,898	$ 812
Loss expected to be reclassified over next twelve months from accumulated other comprehensive loss to interest expense										$ 1,199
Interest rate swap agreement \| Nonrecourse variable rate loans, due August 1, 2019
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)		6.58%
Interest rate swap agreement \| Nonrecourse variable rate loans, due January 2, 2025
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)						4.39%
Number of interest rate swap derivatives \| derivative						3
Interest rate swap agreement \| Nonrecourse variable rate mortgage, due September 1, 2025
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)				3.75%
Number of interest rate swap derivatives \| derivative				2
Interest rate swap agreement \| Nonrecourse Variable Rate Mortgage Due On 1 May 2026 [Member]
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)		4.17%
Nonrecourse Mortgage, Proceeds Excluding Contingent Portion [Member] \| Nonrecourse variable rate mortgage, due September 1, 2025
Debt disclosures
Proceeds from issuance of debt				$ 11,500
Nonrecourse Mortgage, Proceeds Excluding Contingent Portion [Member] \| Interest rate swap agreement \| Nonrecourse variable rate loans, due January 2, 2025
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)						4.43%
Nonrecourse Mortgage, Proceeds Excluding Contingent Portion [Member] \| Interest rate swap agreement \| Nonrecourse variable rate mortgage, due September 1, 2025
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)				3.77%
Notional amount of interest rate swap agreement				$ 11,500
Nonrecourse Mortgage, Contingent Portion [Member] \| Nonrecourse variable rate loans, due January 2, 2025
Debt disclosures
Proceeds held in escrow			$ 1,850
Nonrecourse Mortgage, Contingent Portion [Member] \| Nonrecourse variable rate loans, due January 2, 2025 \| Location 1
Debt disclosures
Leased space \| ft²						102,000
Nonrecourse Mortgage, Contingent Portion [Member] \| Nonrecourse variable rate mortgage, due September 1, 2025
Debt disclosures
Proceeds held in escrow												$ 2,600
Nonrecourse Mortgage, Contingent Portion [Member] \| 4.33%, due August 1, 2030 mortgage loan
Debt disclosures
Proceeds from issuance of debt					$ 25		$ 600	$ 25	$ 2,500
Leased space \| ft²									88,000
Proceeds held in escrow					$ 3,125
Nonrecourse Mortgage, Contingent Portion [Member] \| Interest rate swap agreement \| Nonrecourse variable rate loans, due January 2, 2025
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)						3.88%
Notional amount of interest rate swap agreement						$ 1,850
Nonrecourse Mortgage, Contingent Portion [Member] \| Interest rate swap agreement \| Nonrecourse variable rate mortgage, due September 1, 2025
Debt disclosures
Fixed interest rate pursuant to interest rate swap agreement (as a percent)				3.67%
Notional amount of interest rate swap agreement				$ 2,600
LIBOR \| Nonrecourse variable rate loans, due August 1, 2019
Debt disclosures
Variable interest rate margin (as a percent)		3.08%
LIBOR \| Nonrecourse variable rate loans, due January 2, 2025
Debt disclosures
Variable interest rate margin (as a percent)						1.95%
LIBOR \| Nonrecourse variable rate mortgage, due September 1, 2025
Debt disclosures
Variable interest rate margin (as a percent)				1.65%
LIBOR \| Nonrecourse Variable Rate Mortgage, Refinanced, Due In September 2026 [Member] \| Subsequent events
Debt disclosures
Variable interest rate margin (as a percent)	1.70%
LIBOR \| Nonrecourse Variable Rate Mortgage Due On 1 May 2026 [Member]
Debt disclosures
Variable interest rate margin (as a percent)		2.00%