Financial Instruments and Fair Values - Summary of the Carrying and Estimated Fair Values of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in accounts payable and accrued expenses	$ 0	$ 436
Carrying Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	609,299	717,164
Carrying Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	247,114	244,739
Carrying Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	798,248
Carrying Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		463,156
Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	574,238	707,300
Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	251,563	275,723
Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	773,375
Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		460,352
Level 1 | Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 1 | Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 1 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0
Level 1 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		0
Level 2 | Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 2 | Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	251,563	275,723
Level 2 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0
Level 2 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		0
Level 3 | Estimated Fair Value | Mortgages
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	574,238	707,300
Level 3 | Estimated Fair Value | Exchangeable notes | Senior unsecured notes - exchangeable
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Level 3 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C, D, E and F
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	773,375
Level 3 | Estimated Fair Value | Senior notes | Senior unsecured notes - Series A, B, C and D
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value		460,352
Unsecured term loan facility | Carrying Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	264,023	263,662
Unsecured term loan facility | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
Unsecured term loan facility | Level 1 | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Unsecured term loan facility | Level 2 | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Unsecured term loan facility | Level 3 | Estimated Fair Value | Term loan facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	265,000	265,000
Interest Rate Swap | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	9,944	0
Interest rate swaps included in accounts payable and accrued expenses	0	436
Interest Rate Swap | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	9,944	0
Interest rate swaps included in accounts payable and accrued expenses	0	436
Interest Rate Swap | Level 1 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	0
Interest rate swaps included in accounts payable and accrued expenses	0	0
Interest Rate Swap | Level 2 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	9,944	0
Interest rate swaps included in accounts payable and accrued expenses	0	436
Interest Rate Swap | Level 3 | Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest rate swaps included in prepaid expenses and other assets	0	0
Interest rate swaps included in accounts payable and accrued expenses	$ 0	$ 0