Fair Value Measurements - Financial Instruments Not Carried at Fair Value (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Carrying value
Fair value of financial assets and liabilities
Mortgages payable assumed in connection with acquisitions	$ 822.0	$ 842.3
Notes and bonds payable	17,417.9	14,114.2
Fair value
Fair value of financial assets and liabilities
Mortgages payable assumed in connection with acquisitions	806.1	810.4
Notes and bonds payable	15,478.2	12,522.8
Mortgages payable
Fair value of financial assets and liabilities
Unamortized net premiums	2.8	12.4
Deferred financing costs	0.6	0.8
Notes and bonds payable
Fair value of financial assets and liabilities
Unamortized net premiums	147.5	224.6
Deferred financing costs	78.4	$ 60.7
Basis adjustment on interest rate swap designated as fair value hedge	$ (4.4)

Amount, after accumulated amortization, of debt premium.

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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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- Definition

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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Net fair value of all derivative instruments designated as fair value hedging instruments.

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- Definition

Fair value portion of contractual obligation to pay money on demand or on fixed or determinable dates.

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- Definition

Fair value portion of notes payable.

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