Fair value measurements - Assets and Liabilities on Recurring and Nonrecurring Basis (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($) transfer	Dec. 31, 2023 USD ($)
Assets and liabilities measured at fair value
Transfers in Fair Value Hierarchy | transfer	0
Disposal Group, Including Assets Held For Sale Not Qualifying As Discontinued Operations, Net Assets	$ 272,700	$ 191,400
Investments	1,519,327	1,449,518
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Secured notes payable	145,000	119,662
Unsecured senior notes payable	12,092,012	11,096,028
Unsecured senior lines of credit	454,589	99,952
Book value
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Secured notes payable	145,000	119,662
Unsecured senior notes payable	12,092,012	11,096,028
Book value | Commercial Paper
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Commercial paper program	454,589	99,952
Book value | Unsecured senior line of credit
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Unsecured senior lines of credit	0	0
Fair Value | Fair value measured on nonrecurring basis
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Real Estate, Held-for-Sale	70,566	133,885
Secured notes payable, fair value	144,398	118,660
Unsecured senior notes payable, fair value	10,927,583	9,708,930
Fair Value | Fair value measured on nonrecurring basis | Commercial Paper
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Commercial paper, fair value disclosure	454,575	99,915
Fair Value | Fair value measured on nonrecurring basis | Unsecured senior line of credit
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Unsecured senior lines of credit, fair value	0	0
Fair Value | Fair value measured on nonrecurring basis | Quoted prices in active markets for identical assets (Level 1)
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
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
Fair Value | Fair value measured on nonrecurring basis | Quoted prices in active markets for identical assets (Level 1) | Commercial Paper
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Commercial paper, fair value disclosure	0	0
Fair Value | Fair value measured on nonrecurring basis | Quoted prices in active markets for identical assets (Level 1) | Unsecured senior line of credit
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Unsecured senior lines of credit, fair value	0	0
Fair Value | Fair value measured on nonrecurring basis | Significant other observable inputs (Level 2)
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Long-Lived Asset, Held-for-Sale, Fair Value Disclosure	0	0
Secured notes payable, fair value	144,398	118,660
Unsecured senior notes payable, fair value	10,927,583	9,708,930
Fair Value | Fair value measured on nonrecurring basis | Significant other observable inputs (Level 2) | Commercial Paper
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Commercial paper, fair value disclosure	454,575	99,915
Fair Value | Fair value measured on nonrecurring basis | Significant other observable inputs (Level 2) | Unsecured senior line of credit
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Unsecured senior lines of credit, fair value	0	0
Fair Value | Fair value measured on nonrecurring basis | Significant unobservable input (Level 3)
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Long-Lived Asset, Held-for-Sale, Fair Value Disclosure	70,566	133,885
Secured notes payable, fair value	0	0
Unsecured senior notes payable, fair value	0	0
Fair Value | Fair value measured on nonrecurring basis | Significant unobservable input (Level 3) | Commercial Paper
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Commercial paper, fair value disclosure	0	0
Fair Value | Fair value measured on nonrecurring basis | Significant unobservable input (Level 3) | Unsecured senior line of credit
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Unsecured senior lines of credit, fair value	0	0
Investments in publicly traded companies
Assets and liabilities measured at fair value
Investments at fair value	152,426	159,566
Investments in publicly traded companies | Fair Value | Fair value measured on recurring basis
Assets and liabilities measured at fair value
Investments at fair value	152,426	159,566
Investments in publicly traded companies | Fair Value | Fair value measured on recurring basis | Quoted prices in active markets for identical assets (Level 1)
Assets and liabilities measured at fair value
Investments at fair value	152,426	159,566
Investments in publicly traded companies | Fair Value | Fair value measured on recurring basis | Significant other observable inputs (Level 2)
Assets and liabilities measured at fair value
Investments at fair value	0	0
Investments in publicly traded companies | Fair Value | Fair value measured on recurring basis | Significant unobservable input (Level 3)
Assets and liabilities measured at fair value
Investments at fair value	0	0
Investments in privately held entities that report NAV
Assets and liabilities measured at fair value
Investments at fair value	656,425	671,532
Entities without observable price changes | Investments in privately held entities that do not report NAV
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Investments in privately held entities that do not report fair value, book value	407,261	368,654
Entities without observable price changes | Investments in privately held entities that do not report NAV | Fair Value | Fair value measured on nonrecurring basis
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Investments in privately held entities that do not report fair value, book value	180,833	188,689
Entities without observable price changes | Investments in privately held entities that do not report NAV | Fair Value | Fair value measured on nonrecurring basis | Quoted prices in active markets for identical assets (Level 1)
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Investments in privately held entities that do not report fair value, book value	0	0
Entities without observable price changes | Investments in privately held entities that do not report NAV | Fair Value | Fair value measured on nonrecurring basis | Significant other observable inputs (Level 2)
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Investments in privately held entities that do not report fair value, book value	165,507	174,268
Entities without observable price changes | Investments in privately held entities that do not report NAV | Fair Value | Fair value measured on nonrecurring basis | Significant unobservable input (Level 3)
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Investments in privately held entities that do not report fair value, book value	$ 15,326	$ 14,421