Fair value measurements - Assets and Liabilities on Recurring and Nonrecurring Basis (Details) $ in Thousands	3 Months Ended
Mar. 31, 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	$ 179,300	$ 191,400
Investments	1,511,588	1,449,518
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Secured notes payable	130,050	119,662
Unsecured senior notes payable	12,087,113	11,096,028
Unsecured senior lines of credit	0	99,952
Book value
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Secured notes payable	130,050	119,662
Unsecured senior notes payable	12,087,113	11,096,028
Book value \| Commercial Paper
Fair Value Measurements, Nonrecurring Value Measurement [Abstract]
Commercial paper program	0	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	118,530	133,885
Secured notes payable, fair value	129,619	118,660
Unsecured senior notes payable, fair value	10,509,910	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	0	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	129,619	118,660
Unsecured senior notes payable, fair value	10,509,910	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	0	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	118,530	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	174,521	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	174,521	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	174,521	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	672,129	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	382,408	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	182,596	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	166,688	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	$ 15,908	$ 14,421

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Disposal Group, Including Assets Held For Sale Not Qualifying As Discontinued Operations, Net Assets

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- Definition

Including the current and noncurrent portions, fair value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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Transfers in Fair Value Hierarchy

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- Definition

Fair value portion of assets classified as held for sale.

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Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI), classified as current.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI) and investment in equity security without readily determinable fair value.

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Amount of investment in equity security without readily determinable fair value.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Fair value portion of contractual arrangement with a lender under which borrowings can be made up to a specific amount at any point in time.

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Fair value portion of notes payable.

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Amount of investment in land and building held for sale. Excludes real estate considered inventory.

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Carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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Carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion. Senior note holders are paid off in full before any payments are made to junior note holders.

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