Notes Payable, Revolving Credit Facility, Interest and Amortization of Deferred Debt Costs - Scheduled Maturities of Debt, Including Scheduled Principal Amortization (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Balloon Payments
October 1 through December 31, 2019	$ 0
2020	61,163
2021	11,012
2022	36,503
2023	84,225
2024	66,645
Thereafter	497,257
Principal amount	756,805
Scheduled Principal Amortization
October 1 through December 31, 2019	7,384
2020	28,536
2021	28,333
2022	28,923
2023	29,313
2024	27,908
Thereafter	115,902
Principal amount	266,299
Total
October 1 through December 31, 2019	7,384
2020	89,699
2021	39,345
2022	65,426
2023	113,538
2024	94,553
Thereafter	613,159
Principal amount	1,023,104	$ 1,000,000
Unamortized deferred debt costs	8,376	10,300
Net	1,014,728
Debt Instrument [Line Items]
Outstanding line of credit	$ 0	45,329
Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Outstanding line of credit		$ 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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