Debt - Narratives (Details)		1 Months Ended	3 Months Ended		6 Months Ended
	Jan. 19, 2017	Jan. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 EUR (€)	Jun. 08, 2017 USD ($)	Jun. 08, 2017 EUR (€)	Feb. 22, 2017 USD ($)	Feb. 22, 2017 EUR (€)	Dec. 31, 2016 USD ($)
Revolving Line Of Credit
Line of credit, maximum borrowing amount			$ 2,350,000,000.00		$ 2,350,000,000.00
Unsecured revolving credit facility			165,501,000		165,501,000							$ 676,715,000
Debt issuance costs			16,852,000		$ 16,852,000
Non Recourse Mortgage
Debt instrument maturity date, range start					Aug. 01, 2017
Debt instrument maturity date, range end					Jun. 01, 2027
Repayments of non recourse mortgage loan					$ 287,813,000	$ 43,905,000
Prepayments of mortgage principal					100,599,000	67,496,000
Increase in value of balance sheet item due to foreign currency translation			27,957,000	$ (44,208,000)	42,707,000	$ (30,175,000)
Unamortized discount			12,631,000		12,631,000
Merged Entities
Non Recourse Mortgage
Unamortized discount			900,000		$ 900,000
Fixed interest rate | Minimum
Non Recourse Mortgage
Mortgage loan on real estate, minimum interest rate					2.00%
Fixed interest rate | Maximum
Non Recourse Mortgage
Mortgage loan on real estate, minimum interest rate					7.80%
Variable interest rate | Minimum
Non Recourse Mortgage
Mortgage loan on real estate, minimum interest rate					0.90%
Variable interest rate | Maximum
Non Recourse Mortgage
Mortgage loan on real estate, minimum interest rate					6.90%
Revolving Credit Facility
Revolving Line Of Credit
Line of credit, maximum borrowing amount										$ 1,850,000,000.00		1,500,000,000.0
Line of credit, amount available in foreign currency			1,000,000,000.0		$ 1,000,000,000.0							750,000,000
Amount available for swing line loan			75,000,000.0		75,000,000.0							50,000,000
Amount available for letters of credit			50,000,000.0		50,000,000.0							50,000,000
Line of credit facility, available			1,300,000,000		1,300,000,000
Letters of credit outstanding, amount			100,000		$ 100,000
Debt Instrument borrowing capacity fee (percentage)					0.20%
Revolving Credit Facility | Other assets, net
Revolving Line Of Credit
Debt issuance costs										8,500,000
Term Loan
Revolving Line Of Credit
Line of credit, maximum borrowing amount											€ 236,300,000.0	250,000,000
Unsecured revolving credit facility										250,000,000	236,300,000
Debt issuance costs			300,000		$ 300,000							100,000
Debt Instrument borrowing capacity fee (percentage)					0.20%
Non Recourse Mortgage
Unamortized discount			1,300,000		$ 1,300,000
Delayed Draw term loan
Revolving Line Of Credit
Line of credit, maximum borrowing amount | €											€ 100,000,000.0
Unsecured revolving credit facility								$ 100,000,000.0	€ 88,700,000.0
Senior Unsecured Notes
Maturity Date					Feb. 22, 2022
Amended Revolver
Revolving Line Of Credit
Line of credit, maximum borrowing amount										$ 1,500,000,000.0
Senior Unsecured Notes
Revolving Line Of Credit
Debt issuance costs			15,400,000		$ 15,400,000							12,100,000
Senior Unsecured Notes
Principal Amount			2,400,000,000.0		2,400,000,000.0
Non Recourse Mortgage
Unamortized discount			10,400,000		$ 10,400,000							$ 7,800,000
Senior Unsecured Notes | Government Bond Yield | Minimum
Senior Unsecured Notes
Variable interest rate (percentage)					0.30%
Senior Unsecured Notes | Government Bond Yield | Maximum
Senior Unsecured Notes
Variable interest rate (percentage)					0.35%
Senior Unsecured Notes | 2.25% Senior Notes
Revolving Line Of Credit
Debt issuance costs			$ 4,000,000		$ 4,000,000
Senior Unsecured Notes
Principal Amount | €							€ 500,000,000
Coupon Rate	2.25%				2.25%
Issue Date					Jan. 19, 2017
Price of Par Value			99.448%		99.448%		99.448%
Debt Instrument, Term	7 years 6 months
Maturity Date					Jul. 19, 2024
Secured Debt | International Properties
Non Recourse Mortgage
Repayments of non recourse mortgage loan		$ 243,800,000
Secured Debt | International Properties | Noncontrolling interest
Non Recourse Mortgage
Repayments of non recourse mortgage loan		$ 90,300,000			$ 16,800,000
Weighted average interest rate		5.40%
Non-Recourse Debt
Non Recourse Mortgage
Prepayments of mortgage principal					100,600,000
Gain on the extinguishment of debt					2,400,000
Increase in value of balance sheet item due to foreign currency translation					$ 138,600,000
Non-Recourse Debt | Properties disposed of by sale
Non Recourse Mortgage
Weighted average interest rate			5.30%		5.30%		5.30%
Prepayments of mortgage principal					$ 18,500,000