Fair Value of Financial Instruments - Fair Value, by Balance Sheet Grouping (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage notes payable	$ 1,366,818	$ 1,129,807
Mortgage notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Mortgage notes payable	1,366,818	1,129,807
Deferred financing costs	15,510	9,737
Term Loan	1,382,381	1,140,113
Significant Unobservable Inputs Level 3 \| Mortgage notes payable \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,366,818	1,129,807
Mortgage notes payable	1,400,000	1,100,000
Mortgage discount	100	600
Deferred financing costs	15,500	9,700
Significant Unobservable Inputs Level 3 \| Mortgage notes payable \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	1,439,910	1,157,710
Significant Unobservable Inputs Level 3 \| Line of Credit \| Revolving Credit Facility \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	101,405	363,894
Significant Unobservable Inputs Level 3 \| Line of Credit \| Revolving Credit Facility \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	101,437	365,591
Significant Unobservable Inputs Level 3 \| Line of Credit \| Term Facility \| Credit Facility \| Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	389,885	278,727
Significant Unobservable Inputs Level 3 \| Line of Credit \| Term Facility \| Credit Facility \| Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt, fair value	396,867	283,558
KeyBank National Association \| Unsecured debt \| Term Facility \| Credit Facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred financing costs	2,634	3,342
Term Loan	$ 392,519	$ 282,069

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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Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

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Amount, after accumulated amortization, of debt discount (premium).

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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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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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