Mortgage and Other Indebtedness - Consolidated Indebtedness by Type of Debt (Details) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Participating Mortgage Loans [Line Items]
Principal	$ 1,548,770,000	$ 1,700,650,000
Unamortized Net Premiums	6,566,000	9,196,000
Unamortized Debt Issuance Costs	(12,035,000)	(10,607,000)
Long-term debt	1,543,301,000	1,699,239,000
Revolving Credit Facility
Participating Mortgage Loans [Line Items]
Principal	45,600,000	60,100,000
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(3,796,000)	(1,895,000)
Long-term debt	41,804,000	58,205,000
Line of credit facility, remaining borrowing capacity	$ 449,500,000	$ 373,800,000
Basis spread on variable rate (as percent)	1.15%	1.35%
Interest rate, effective percentage (as percent)	3.65%	2.91%
Senior Unsecured Notes \| Fixed Rate Debt
Participating Mortgage Loans [Line Items]
Principal	$ 550,000,000	$ 550,000,000
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(4,864,000)	(5,599,000)
Long-term debt	$ 545,136,000	$ 544,401,000
Senior Unsecured Notes \| Fixed Rate Debt \| Minimum
Participating Mortgage Loans [Line Items]
Interest rate during period (as percent)	4.00%	4.00%
Senior Unsecured Notes \| Fixed Rate Debt \| Maximum
Participating Mortgage Loans [Line Items]
Interest rate during period (as percent)	4.57%	4.57%
Unsecured Debt
Participating Mortgage Loans [Line Items]
Principal	$ 345,000,000	$ 400,000,000
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(2,470,000)	(1,759,000)
Long-term debt	$ 342,530,000	$ 398,241,000
Unsecured Debt \| Unsecured Term Loans, Maturing July 2021
Participating Mortgage Loans [Line Items]
Basis spread on variable rate (as percent)	1.30%	1.30%
Interest rate, effective percentage (as percent)	3.80%	2.86%
Debt instrument, face amount	$ 95,000,000	$ 200,000,000
Unsecured Debt \| Unsecured Term Loans, Maturing October 2025
Participating Mortgage Loans [Line Items]
Basis spread on variable rate (as percent)	2.00%
Interest rate, effective percentage (as percent)	4.50%
Debt instrument, face amount	$ 250,000,000
Unsecured Debt \| Unsecured Term Loans, Maturing October 2022
Participating Mortgage Loans [Line Items]
Basis spread on variable rate (as percent)		1.60%
Interest rate, effective percentage (as percent)		3.16%
Debt instrument, face amount		$ 200,000,000
Mortgages \| Fixed Rate Debt
Participating Mortgage Loans [Line Items]
Principal	534,679,000	576,927,000
Unamortized Net Premiums	6,566,000	9,196,000
Unamortized Debt Issuance Costs	(584,000)	(755,000)
Long-term debt	$ 540,661,000	$ 585,368,000
Mortgages \| Fixed Rate Debt \| Minimum
Participating Mortgage Loans [Line Items]
Interest rate during period (as percent)	3.78%	3.78%
Mortgages \| Fixed Rate Debt \| Maximum
Participating Mortgage Loans [Line Items]
Interest rate during period (as percent)	6.78%	6.78%
Mortgages \| Variable Rate Debt
Participating Mortgage Loans [Line Items]
Principal	$ 73,491,000	$ 113,623,000
Unamortized Net Premiums	0	0
Unamortized Debt Issuance Costs	(321,000)	(599,000)
Long-term debt	$ 73,170,000	$ 113,024,000
Mortgages \| Variable Rate Debt \| Minimum
Participating Mortgage Loans [Line Items]
Interest rate during period (as percent)	4.00%	3.16%
Basis spread on variable rate (as percent)	1.50%	1.60%
Mortgages \| Variable Rate Debt \| Maximum
Participating Mortgage Loans [Line Items]
Interest rate during period (as percent)	4.10%	3.81%
Basis spread on variable rate (as percent)	1.60%	2.25%

Long-term Debt, Principal Balance

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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No definition available.

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Face (par) amount of debt instrument at time of issuance.

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The average effective interest rate during the reporting period.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Amount, after accumulated amortization, of debt premium.

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Amount, after accumulated amortization, of debt issuance costs related to line of credit arrangements. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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