Financial Instruments and Fair Values - Summary of the Carrying and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap included in accounts payable and accrued expenses	$ 4,887	$ 8,849
Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap included in accounts payable and accrued expenses	4,900
Carrying Value | Unsecured term loan facilities | Revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	388,095	387,561
Carrying Value | Mortgage notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	773,925	775,929
Carrying Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E, F, G and H
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	973,320	973,159
Carrying Value | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap included in accounts payable and accrued expenses	4,887	8,849
Estimated Fair Value | Unsecured term loan facilities | Revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	390,000	390,000
Estimated Fair Value | Mortgage notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	790,407	808,294
Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E, F, G and H
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	999,220	1,039,857
Estimated Fair Value | Level 1 | Unsecured term loan facilities | Revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Estimated Fair Value | Level 1 | Mortgage notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Estimated Fair Value | Level 1 | Senior notes | Senior unsecured notes - Series A, B, C, D, E, F, G and H
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Estimated Fair Value | Level 2 | Unsecured term loan facilities | Revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Estimated Fair Value | Level 2 | Mortgage notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Estimated Fair Value | Level 2 | Senior notes | Senior unsecured notes - Series A, B, C, D, E, F, G and H
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Estimated Fair Value | Level 3 | Unsecured term loan facilities | Revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	390,000	390,000
Estimated Fair Value | Level 3 | Mortgage notes payable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	790,407	808,294
Estimated Fair Value | Level 3 | Senior notes | Senior unsecured notes - Series A, B, C, D, E, F, G and H
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	999,220	1,039,857
Estimated Fair Value | Interest rate swap
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap included in accounts payable and accrued expenses	4,887	8,849
Estimated Fair Value | Interest rate swap | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap included in accounts payable and accrued expenses	0	0
Estimated Fair Value | Interest rate swap | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap included in accounts payable and accrued expenses	4,887	8,849
Estimated Fair Value | Interest rate swap | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swap included in accounts payable and accrued expenses	$ 0	$ 0