Debt (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) extension	Sep. 30, 2021 CAD ($) extension	Sep. 30, 2021 EUR (€) extension	Sep. 30, 2021 GBP (£) extension	Dec. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)
Mortgages, Senior Notes and Term Loans
Debt Instrument [Line Items]
Carrying Amount	$ 2,717,703				$ 2,664,218
Estimated Fair Value	2,818,478				2,827,440
Less: unamortized deferred financing costs	(11,446)				(15,952)
Long-term Debt, Total	2,706,257				2,648,266
Mortgage Loans | 2013 Mortgage Loans
Debt Instrument [Line Items]
Carrying Amount	271,415				276,693
Estimated Fair Value	$ 279,127				285,772
Mortgage Loans | Senior note
Debt Instrument [Line Items]
Contractual Interest Rate	3.81%	3.81%	3.81%	3.81%
Effective Interest Rate as of September 30, 2021	4.14%	4.14%	4.14%	4.14%
Carrying Amount	$ 169,415				174,693
Estimated Fair Value	$ 174,497				180,807
Mortgage Loans | Mezzanine A
Debt Instrument [Line Items]
Contractual Interest Rate	7.38%	7.38%	7.38%	7.38%
Effective Interest Rate as of September 30, 2021	7.55%	7.55%	7.55%	7.55%
Carrying Amount	$ 70,000				70,000
Estimated Fair Value	$ 71,750				71,925
Mortgage Loans | Mezzanine B
Debt Instrument [Line Items]
Contractual Interest Rate	11.50%	11.50%	11.50%	11.50%
Effective Interest Rate as of September 30, 2021	11.75%	11.75%	11.75%	11.75%
Carrying Amount					32,000	$ 32,000
Estimated Fair Value	$ 32,880				33,040
Senior Notes | Senior Unsecured Notes
Debt Instrument [Line Items]
Carrying Amount	1,818,500				1,866,200
Estimated Fair Value	$ 1,914,742				2,022,950
Senior Notes | Series D 1.62% notes due 2031
Debt Instrument [Line Items]
Contractual Interest Rate	1.62%	1.62%	1.62%	1.62%
Effective Interest Rate as of September 30, 2021	1.67%	1.67%	1.67%	1.67%
Carrying Amount	$ 463,200				488,640
Estimated Fair Value	$ 454,515				488,640
Face amount of debt | €			€ 400,000,000
Senior Notes | Series E 1.65% notes due 2033
Debt Instrument [Line Items]
Contractual Interest Rate	1.65%	1.65%	1.65%	1.65%
Effective Interest Rate as of September 30, 2021	1.70%	1.70%	1.70%	1.70%
Carrying Amount	$ 405,300				427,560
Estimated Fair Value	$ 399,727				427,560
Face amount of debt | €			€ 350,000,000
Senior Notes | Series C notes
Debt Instrument [Line Items]
Contractual Interest Rate	4.10%	4.10%	4.10%	4.10%
Effective Interest Rate as of September 30, 2021	4.15%	4.15%	4.15%	4.15%
Carrying Amount	$ 350,000				350,000
Estimated Fair Value	$ 385,000				400,750
Senior Notes | Series A notes
Debt Instrument [Line Items]
Contractual Interest Rate	4.68%	4.68%	4.68%	4.68%
Effective Interest Rate as of September 30, 2021	4.77%	4.77%	4.77%	4.77%
Carrying Amount	$ 200,000				200,000
Estimated Fair Value	$ 220,500				231,000
Senior Notes | Series B notes
Debt Instrument [Line Items]
Contractual Interest Rate	4.86%	4.86%	4.86%	4.86%
Effective Interest Rate as of September 30, 2021	4.92%	4.92%	4.92%	4.92%
Carrying Amount	$ 400,000				400,000
Estimated Fair Value	455,000				475,000
Term Loans | Total 2020 Senior Unsecured Term Loan A Facility
Debt Instrument [Line Items]
Carrying Amount	322,124				521,325
Estimated Fair Value	$ 319,709				518,718
Term Loans | 2020 Senior Unsecured Term Loan Tranche A-1
Debt Instrument [Line Items]
Effective Interest Rate as of September 30, 2021	1.41%	1.41%	1.41%	1.41%
Carrying Amount	$ 125,000				325,000
Estimated Fair Value	$ 124,063				323,375
Term Loans | 2020 Senior Unsecured Term Loan Tranche A-1 | LIBOR
Debt Instrument [Line Items]
Contractual Interest Rate	0.95%
Term Loans | 2020 Senior Unsecured Term Loan Tranche A-2
Debt Instrument [Line Items]
Effective Interest Rate as of September 30, 2021	1.51%	1.51%	1.51%	1.51%
Carrying Amount	$ 197,124				196,325
Estimated Fair Value	$ 195,646				195,343
Face amount of debt		$ 250,000,000
Term Loans | 2020 Senior Unsecured Term Loan Tranche A-2 | CDOR
Debt Instrument [Line Items]
Contractual Interest Rate	0.95%
Term Loans | Twenty Twenty Senior Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Carrying Amount	$ 305,664				0
Estimated Fair Value	$ 304,900				0
Term Loans | 2020 Senior Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Effective Interest Rate as of September 30, 2021	1.53%	1.53%	1.53%	1.53%
Carrying Amount	$ 92,296				0
Estimated Fair Value	$ 92,065				0
Term Loans | 2020 Senior Unsecured Revolving Credit Facility | SONIA
Debt Instrument [Line Items]
Contractual Interest Rate	0.85%
Term Loans | 2020 Senior Unsecured Revolving Credit Facility
Debt Instrument [Line Items]
Effective Interest Rate as of September 30, 2021	1.56%	1.56%	1.56%	1.56%
Carrying Amount	$ 170,000				0
Estimated Fair Value	$ 169,575				0
Term Loans | 2020 Senior Unsecured Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Contractual Interest Rate	0.85%
Line of Credit | 2020 Senior Unsecured Term Loan Tranche A-2 | Revolving Credit Facility
Debt Instrument [Line Items]
Revolver borrowing capacity | £				£ 68,500,000
Line of Credit | 2020 Senior Unsecured Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Effective Interest Rate as of September 30, 2021	1.91%	1.91%	1.91%	1.91%
Carrying Amount	$ 43,368				0
Estimated Fair Value	$ 43,260				$ 0
Number of extensions | extension	2	2	2	2
Extension term	6 months
Revolver borrowing capacity		$ 55,000,000.0
Line of Credit | 2020 Senior Unsecured Revolving Credit Facility | CDOR | Revolving Credit Facility
Debt Instrument [Line Items]
Contractual Interest Rate	0.85%