Notes Payable, Revolving Credit Facility, Interest and Amortization of Deferred Debt Costs - Scheduled Maturities of Debt, Including Scheduled Principal Amortization (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Balloon Payments
April 1 through December 31, 2019	$ 12,060
2020	61,163
2021	11,012
2022	76,502
2023	84,225
2024	66,637
Thereafter	440,667
Principal amount	752,266
Scheduled Principal Amortization
April 1 through December 31, 2019	22,312
2020	28,538
2021	28,335
2022	28,925
2023	29,316
2024	27,882
Thereafter	115,901
Principal amount	281,209
Total
April 1 through December 31, 2019	34,372
2020	89,701
2021	39,347
2022	105,427
2023	113,541
2024	94,519
Thereafter	556,568
Principal amount	1,033,475	$ 1,000,000
Unamortized deferred debt costs	10,354	10,300
Net	1,023,121
Debt Instrument [Line Items]
Outstanding line of credit	38,465	45,329
Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Outstanding line of credit	$ 40,000	$ 47,000

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Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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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.

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Amount of payment greater than the preceding installment payments to be paid at final maturity date of debt.

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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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