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Risk Management and Use of Derivative Financial Instruments - Narratives (Details) £ in Millions, ¥ in Billions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) offering	Jun. 30, 2019 USD ($)	Jun. 30, 2020 JPY (¥)	Jun. 30, 2020 EUR (€)	Jun. 30, 2020 GBP (£)	Mar. 27, 2020 USD ($)	Feb. 20, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 19, 2019
Summary of Derivative Instruments
Net collateral posted for derivatives	$ 0		$ 0							$ 0
Amount of gain (loss) recognized on derivatives in other comprehensive income (loss)	(9,397,000)	$ (2,413,000)	$ 3,900,000	$ 480,000
Derivative, remaining maturity			62 months
Total credit exposure on derivatives	23,000,000.0		$ 23,000,000.0
Derivatives, net liability position	11,000,000.0		11,000,000.0							9,600,000
Aggregate termination value for immediate settlement	11,600,000		11,600,000							9,900,000
Debt outstanding	314,518,000		314,518,000							201,267,000
Other comprehensive income foreign currency gain (loss)	(62,900,000)	(30,500,000)	22,000,000.0	13,600,000
Unsecured Revolving Credit Facility
Summary of Derivative Instruments
Debt outstanding	22,366,000		22,366,000							201,267,000
Unsecured Term Loans
Summary of Derivative Instruments
Debt outstanding	292,152,000		292,152,000							0
EUR \| Unsecured Revolving Credit Facility
Summary of Derivative Instruments
Debt outstanding	0		0							131,438,000
EUR \| Unsecured Term Loans
Summary of Derivative Instruments
Debt outstanding	108,061,000		108,061,000			€ 96,500,000		$ 105,900,000		0
JPY \| Unsecured Revolving Credit Facility
Summary of Derivative Instruments
Debt outstanding	22,366,000		22,366,000		¥ 2.4					22,295,000
GBP \| Unsecured Revolving Credit Facility
Summary of Derivative Instruments
Debt outstanding	0		0							47,534,000
GBP \| Unsecured Term Loans
Summary of Derivative Instruments
Debt outstanding	184,091,000		$ 184,091,000				£ 150.0		$ 193,100,000	$ 0
Unsecured senior notes
Summary of Derivative Instruments
Number of offerings completed \| offering			5
Principal amount	$ 4,400,000,000		$ 4,400,000,000
Unsecured senior notes \| 2.0% Senior Notes due 2023
Summary of Derivative Instruments
Principal amount \| €						€ 500,000,000.0
Coupon rate (percentage)	2.00%		2.00%		2.00%	2.00%	2.00%
Unsecured senior notes \| 2.25% Senior Notes due 2024
Summary of Derivative Instruments
Principal amount \| €						€ 500,000,000.0
Coupon rate (percentage)	2.25%		2.25%		2.25%	2.25%	2.25%
Unsecured senior notes \| 2.250% Senior Notes due 2026
Summary of Derivative Instruments
Principal amount \| €						€ 500,000,000.0
Coupon rate (percentage)	2.25%		2.25%		2.25%	2.25%	2.25%
Unsecured senior notes \| 2.125% Senior Notes due 2027
Summary of Derivative Instruments
Principal amount \| €						€ 500,000,000.0
Coupon rate (percentage)	2.125%		2.125%		2.125%	2.125%	2.125%
Unsecured senior notes \| 1.350% Senior Notes due 2028
Summary of Derivative Instruments
Principal amount \| €						€ 500,000,000.0
Coupon rate (percentage)	1.35%		1.35%		1.35%	1.35%	1.35%				1.35%
Individual Counterparty
Summary of Derivative Instruments
Total credit exposure on derivatives	$ 7,900,000		$ 7,900,000
Interest expense
Summary of Derivative Instruments
Estimated amount reclassified from OCI to expense (gain)			3,000,000.0
Other gains
Summary of Derivative Instruments
Estimated amount reclassified from OCI to expense (gain)			(7,800,000)
Equity Method Investments \| Designated as Cash Flow Hedging Instruments
Summary of Derivative Instruments
Amount of gain (loss) recognized on derivatives in other comprehensive income (loss)	$ (100,000)	$ (1,000,000.0)	$ (500,000)	$ (1,900,000)