Fair value measurements - Assets and Liabilities on Recurring Basis (Details) - USD ($)	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers In Fair Value Hierarchy	$ 0
Investments	1,501,249,000	$ 1,476,985,000
Secured notes payable	0	149,909,000
Unsecured senior notes payable	12,047,394,000	12,094,465,000
Net assets classified as held for sale	581,737,000	371,257,000
Currency Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments in Hedges, Liabilities, at Fair Value	928,000	0
Book Value
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Secured notes payable	0	149,909,000
Unsecured senior notes payable	12,047,394,000	12,094,465,000
Book Value | Commercial paper program
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper program	353,161,000	0
Book Value | Unsecured senior line of credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured senior line of credit and commercial paper	0	0
Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Real Estate, Held-for-Sale	581,737,000	322,662,000
Secured notes payable, fair value		149,413,000
Unsecured senior notes payable, fair value	10,675,433,000	10,472,993,000
Fair Value | Fair value measured on nonrecurring basis | Commercial paper program
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper program, fair value	353,189,000	0
Fair Value | Fair value measured on nonrecurring basis | Unsecured senior line of credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured senior line of credit, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Currency Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments in Hedges, Liabilities, at Fair Value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Asset, Held-for-Sale, Fair Value Disclosure	0	0
Secured notes payable, fair value	0	0
Unsecured senior notes payable, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Fair value measured on nonrecurring basis | Commercial paper program
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper program, fair value	0	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Fair value measured on nonrecurring basis | Unsecured senior line of credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured senior line of credit, fair value	0	0
Significant Other Observable Inputs (Level 2) | Currency Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments in Hedges, Liabilities, at Fair Value	928,000	0
Significant Other Observable Inputs (Level 2) | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Asset, Held-for-Sale, Fair Value Disclosure	0	0
Secured notes payable, fair value		149,413,000
Unsecured senior notes payable, fair value	10,675,433,000	10,472,993,000
Significant Other Observable Inputs (Level 2) | Fair Value | Fair value measured on nonrecurring basis | Commercial paper program
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper program, fair value	353,189,000	0
Significant Other Observable Inputs (Level 2) | Fair Value | Fair value measured on nonrecurring basis | Unsecured senior line of credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured senior line of credit, fair value	0	0
Significant Unobservable Inputs (Level 3) | Currency Swap
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments in Hedges, Liabilities, at Fair Value	0	0
Significant Unobservable Inputs (Level 3) | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-Lived Asset, Held-for-Sale, Fair Value Disclosure	581,737,000	322,662,000
Secured notes payable, fair value	0	0
Unsecured senior notes payable, fair value	0	0
Significant Unobservable Inputs (Level 3) | Fair Value | Fair value measured on nonrecurring basis | Commercial paper program
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Commercial paper program, fair value	0	0
Significant Unobservable Inputs (Level 3) | Fair Value | Fair value measured on nonrecurring basis | Unsecured senior line of credit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unsecured senior line of credit, fair value	0	0
Investments in publicly traded companies
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies	94,928,000	105,667,000
Investments in publicly traded companies | Fair value measured on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies	94,928,000	105,667,000
Investments in publicly traded companies | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies		105,667,000
Investments in publicly traded companies | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value | Fair value measured on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies	94,928,000
Investments in publicly traded companies | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies		0
Investments in publicly traded companies | Significant Other Observable Inputs (Level 2) | Fair Value | Fair value measured on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies	0
Investments in publicly traded companies | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies		0
Investments in publicly traded companies | Significant Unobservable Inputs (Level 3) | Fair Value | Fair value measured on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies	0
Investment in Privately Held Entities that Report NAV
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in publicly traded companies	512,400,000	609,900,000
Investments in privately held entities that do not report NAV | Entities without observable price changes | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in privately held entities that do not report fair value, book value	139,251,000	184,236,000
Investments in privately held entities that do not report NAV | Entities without observable price changes
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in privately held entities that do not report fair value, book value	413,300,000	400,500,000
Investments in privately held entities that do not report NAV | Quoted Prices in Active Markets for Identical Assets (Level 1) | Entities without observable price changes | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in privately held entities that do not report fair value, book value	0	0
Investments in privately held entities that do not report NAV | Significant Other Observable Inputs (Level 2) | Entities without observable price changes | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in privately held entities that do not report fair value, book value	123,238,000
Investments in privately held entities that do not report NAV | Significant Other Observable Inputs (Level 2) | Entities without observable price changes | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in privately held entities that do not report fair value, book value		174,737,000
Investments in privately held entities that do not report NAV | Significant Unobservable Inputs (Level 3) | Entities without observable price changes | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in privately held entities that do not report fair value, book value	$ 16,013,000
Investments in privately held entities that do not report NAV | Significant Unobservable Inputs (Level 3) | Entities without observable price changes | Fair Value | Fair value measured on nonrecurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment in privately held entities that do not report fair value, book value		$ 9,499,000