Debt - Narratives (Details)		3 Months Ended		9 Months Ended
	Oct. 14, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 EUR (€)	Sep. 30, 2020 GBP (£)	Mar. 27, 2020 USD ($)	Feb. 20, 2020 USD ($)	Feb. 20, 2020 EUR (€)	Feb. 20, 2020 GBP (£)	Feb. 19, 2020 USD ($)	Dec. 31, 2019 USD ($)
Senior Unsecured Credit Facility
Maximum borrowing capacity		$ 2,750,000,000		$ 2,750,000,000					$ 2,100,000,000			$ 1,850,000,000
Debt outstanding		488,273,000		488,273,000									$ 201,267,000
Financing cost		20,705,000		20,705,000					10,000,000.0
Non Recourse Mortgage
Debt outstanding balance		4,513,243,000		4,513,243,000									4,390,189,000
Real estate carrying value		12,047,350,000		12,047,350,000									11,916,745,000
Repayments of non recourse mortgage loan				241,332,000	$ 93,872,000
Prepayments of mortgage principal				0	872,799,000
Increase in value of balance sheet item due to foreign currency translation		34,170,000	$ (37,412,000)	(4,183,000)	$ (41,772,000)
Unamortized discount		24,592,000		24,592,000
Merged Entities
Non Recourse Mortgage
Unamortized discount		$ 4,800,000		$ 4,800,000
Fixed interest rate
Non Recourse Mortgage
Weighted average interest rate		4.90%		4.90%		4.90%	4.90%
Variable interest rate
Non Recourse Mortgage
Weighted average interest rate		2.90%		2.90%		2.90%	2.90%
Vacant Properties
Senior Unsecured Credit Facility
Stated interest rate (percentage)		6.90%		6.90%		6.90%	6.90%
Non Recourse Mortgage
Debt outstanding balance		$ 3,000,000.0		$ 3,000,000.0
Accrued interest payable		200,000		200,000
Real estate carrying value		3,700,000		3,700,000
Unsecured senior notes
Senior Unsecured Credit Facility
Financing cost		20,300,000		20,300,000									22,800,000
Principal Amount		4,600,000,000		4,600,000,000
Non Recourse Mortgage
Debt outstanding balance		4,552,000,000.0		4,552,000,000.0									4,433,500,000
Unamortized discount		$ 18,500,000		$ 18,500,000									20,500,000
Unsecured senior notes | Senior Note 2.400% Due 2031 | Subsequent Events
Senior Unsecured Credit Facility
Principal Amount	$ 500,000,000.0
Stated interest rate (percentage)	2.40%
Price of par value (percentage)	99.099%
Debt instrument term (years)	10 years 3 months 18 days
Non-Recourse Debt
Non Recourse Mortgage
Weighted average interest rate		5.00%	4.90%	5.00%	4.90%	5.00%	5.00%
Repayments of non recourse mortgage loan				$ 202,500,000	$ 39,400,000
Unsecured Revolving Credit Facility
Senior Unsecured Credit Facility
Debt outstanding		$ 182,799,000		182,799,000									201,267,000
Line of credit facility, available		1,600,000,000		$ 1,600,000,000
Debt Instrument borrowing capacity fee (percentage)				0.20%
Unsecured Revolving Credit Facility | USD
Senior Unsecured Credit Facility
Maximum borrowing capacity									1,800,000,000
Debt outstanding		160,000,000		$ 160,000,000									0
Unsecured Revolving Credit Facility | GBP
Senior Unsecured Credit Facility
Debt outstanding		0		0									47,534,000
Unsecured Revolving Credit Facility | EUR
Senior Unsecured Credit Facility
Debt outstanding		0		0									131,438,000
Unsecured Term Loans
Senior Unsecured Credit Facility
Debt outstanding		305,474,000		305,474,000									0
Unsecured Term Loans | GBP
Senior Unsecured Credit Facility
Maximum borrowing capacity | £											£ 150,000,000.0
Debt outstanding		192,492,000		192,492,000			£ 150,000,000.0		$ 193,100,000				0
Non Recourse Mortgage
Unamortized discount		1,300,000		1,300,000
Unsecured Term Loans | EUR
Senior Unsecured Credit Facility
Maximum borrowing capacity | €										€ 96,500,000
Debt outstanding		112,982,000		112,982,000		€ 96,500,000		$ 105,900,000					$ 0
Standby Letters of Credit
Senior Unsecured Credit Facility
Line of credit facility, available		20,100,000		20,100,000
Unsecured senior notes
Non Recourse Mortgage
Unamortized discount		$ 18,500,000		$ 18,500,000
Unsecured senior notes | Government bond yield | Minimum
Senior Unsecured Credit Facility
Variable interest rate (percentage)				0.30%
Unsecured senior notes | Government bond yield | Maximum
Senior Unsecured Credit Facility
Variable interest rate (percentage)				0.35%
Non-Recourse Debt
Non Recourse Mortgage
Prepayments of mortgage principal					$ 872,800,000
Increase in value of balance sheet item due to foreign currency translation				$ 129,800,000