Commitments, Contingencies and Off-Balance Sheet Arrangements - Contractual Obligations (Detail) $ in Millions	Sep. 30, 2023 USD ($)
Senior Notes [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, Thereafter	$ 2,550.0
Contractual Obligations, Payments Due by Period, Total	2,550.0
Note Purchase Agreements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2024	425.0
Contractual Obligations, Payments Due by Period, 2025	200.0
Contractual Obligations, Payments Due by Period, 2026	640.0
Contractual Obligations, Payments Due by Period, 2027	478.0
Contractual Obligations, Payments Due by Period, Thereafter	2,205.0
Contractual Obligations, Payments Due by Period, Total	3,948.0
Premium Financing Debt Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2023	279.0
Contractual Obligations, Payments Due by Period, Total	279.0
Interest On Debt [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2023	55.6
Contractual Obligations, Payments Due by Period, 2024	265.2
Contractual Obligations, Payments Due by Period, 2025	251.4
Contractual Obligations, Payments Due by Period, 2026	232.6
Contractual Obligations, Payments Due by Period, 2027	214.1
Contractual Obligations, Payments Due by Period, Thereafter	2,393.8
Contractual Obligations, Payments Due by Period, Total	3,412.7
Total Debt Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2023	334.6
Contractual Obligations, Payments Due by Period, 2024	690.2
Contractual Obligations, Payments Due by Period, 2025	451.4
Contractual Obligations, Payments Due by Period, 2026	872.6
Contractual Obligations, Payments Due by Period, 2027	692.1
Contractual Obligations, Payments Due by Period, Thereafter	7,148.8
Contractual Obligations, Payments Due by Period, Total	10,189.7
Operating Lease Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2023	20.9
Contractual Obligations, Payments Due by Period, 2024	105.2
Contractual Obligations, Payments Due by Period, 2025	87.1
Contractual Obligations, Payments Due by Period, 2026	71.7
Contractual Obligations, Payments Due by Period, 2027	57.7
Contractual Obligations, Payments Due by Period, Thereafter	105.8
Contractual Obligations, Payments Due by Period, Total	448.4
Less Sublease Arrangements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Receivable by Period, 2023	(0.7)
Contractual Obligations, Payments Receivable by Period, 2024	(2.4)
Contractual Obligations, Payments Receivable by Period, 2025	(1.7)
Contractual Obligations, Payments Receivable by Period, 2026	(1.6)
Contractual Obligations, Payments Receivable by Period, 2027	(1.6)
Contractual Obligations, Payments Receivable by Period, Thereafter	(1.9)
Contractual Obligations, Payments Receivable by Period, Total	(9.9)
Outstanding Purchase Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2023	29.7
Contractual Obligations, Payments Due by Period, 2024	98.8
Contractual Obligations, Payments Due by Period, 2025	55.9
Contractual Obligations, Payments Due by Period, 2026	23.1
Contractual Obligations, Payments Due by Period, 2027	19.0
Contractual Obligations, Payments Due by Period, Thereafter	51.7
Contractual Obligations, Payments Due by Period, Total	278.2
Total Contractual Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2023	384.5
Contractual Obligations, Payments Due by Period, 2024	891.8
Contractual Obligations, Payments Due by Period, 2025	592.7
Contractual Obligations, Payments Due by Period, 2026	965.8
Contractual Obligations, Payments Due by Period, 2027	767.2
Contractual Obligations, Payments Due by Period, Thereafter	7,304.4
Contractual Obligations, Payments Due by Period, Total	$ 10,906.4

Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]

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Recorded unconditional purchase obligation due after fourth year.

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Recorded unconditional purchase obligation receivable.

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Recorded unconditional purchase obligation receivable after fourth year.

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Recorded unconditional purchase obligation receivable in fourth year.

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Recorded unconditional purchase obligation receivable in remainder of fiscal year.

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Recorded unconditional purchase obligation receivable in second year.

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Recorded unconditional purchase obligation receivable in third year.

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Recorded unconditional purchase obligation receivable within one year.

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Amount of the recorded obligation to transfer funds in the future for fixed or minimum amounts or quantities of goods or services at fixed or minimum prices (for example, as in take-or-pay contracts or throughput contracts).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 440
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482648/440-10-50-6

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Amount of recorded unconditional purchase obligation to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of recorded unconditional purchase obligation to be paid in remainder of current fiscal year.

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Amount of recorded unconditional purchase obligation to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of recorded unconditional purchase obligation to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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Amount of recorded unconditional purchase obligation to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

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