Commitments, Contingencies and Off-Balance Sheet Arrangements - Contractual Obligations (Detail) $ in Millions	Sep. 30, 2020 USD ($)
Note Purchase Agreements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2020	$ 50.0
Contractual Obligations, Payments Due by Period, 2021	75.0
Contractual Obligations, Payments Due by Period, 2022	200.0
Contractual Obligations, Payments Due by Period, 2023	250.0
Contractual Obligations, Payments Due by Period, 2024	475.0
Contractual Obligations, Payments Due by Period, Thereafter	3,348.0
Contractual Obligations, Payments Due by Period, Total	4,398.0
Premium Financing Debt Facility [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2020	193.0
Contractual Obligations, Payments Due by Period, Total	193.0
Interest On Debt [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2020	40.8
Contractual Obligations, Payments Due by Period, 2021	189.3
Contractual Obligations, Payments Due by Period, 2022	183.6
Contractual Obligations, Payments Due by Period, 2023	174.7
Contractual Obligations, Payments Due by Period, 2024	158.0
Contractual Obligations, Payments Due by Period, Thereafter	745.3
Contractual Obligations, Payments Due by Period, Total	1,491.7
Total Debt Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2020	283.8
Contractual Obligations, Payments Due by Period, 2021	264.3
Contractual Obligations, Payments Due by Period, 2022	383.6
Contractual Obligations, Payments Due by Period, 2023	424.7
Contractual Obligations, Payments Due by Period, 2024	633.0
Contractual Obligations, Payments Due by Period, Thereafter	4,093.3
Contractual Obligations, Payments Due by Period, Total	6,082.7
Operating Lease Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2020	29.7
Contractual Obligations, Payments Due by Period, 2021	107.7
Contractual Obligations, Payments Due by Period, 2022	85.2
Contractual Obligations, Payments Due by Period, 2023	66.7
Contractual Obligations, Payments Due by Period, 2024	47.4
Contractual Obligations, Payments Due by Period, Thereafter	90.2
Contractual Obligations, Payments Due by Period, Total	426.9
Less Sublease Arrangements [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Receivable by Period, 2020	(0.1)
Contractual Obligations, Payments Receivable by Period, 2021	(0.3)
Contractual Obligations, Payments Receivable by Period, 2022	(0.3)
Contractual Obligations, Payments Receivable by Period, 2023	(0.2)
Contractual Obligations, Payments Receivable by Period, 2024	(0.2)
Contractual Obligations, Payments Receivable by Period, Thereafter	(0.7)
Contractual Obligations, Payments Receivable by Period, Total	(1.8)
Outstanding Purchase Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2020	15.5
Contractual Obligations, Payments Due by Period, 2021	44.9
Contractual Obligations, Payments Due by Period, 2022	30.4
Contractual Obligations, Payments Due by Period, 2023	13.7
Contractual Obligations, Payments Due by Period, 2024	8.7
Contractual Obligations, Payments Due by Period, Thereafter	31.0
Contractual Obligations, Payments Due by Period, Total	144.2
Total Contractual Obligations [Member]
Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]
Contractual Obligations, Payments Due by Period, 2020	328.9
Contractual Obligations, Payments Due by Period, 2021	416.6
Contractual Obligations, Payments Due by Period, 2022	498.9
Contractual Obligations, Payments Due by Period, 2023	504.9
Contractual Obligations, Payments Due by Period, 2024	688.9
Contractual Obligations, Payments Due by Period, Thereafter	4,213.8
Contractual Obligations, Payments Due by Period, Total	$ 6,652.0

Commitments Contingencies And Off Balance Sheet Arrangements [Line Items]

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- Definition

Recorded unconditional purchase obligation due after fourth year.

+ References

No definition available.

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- Definition

Recorded unconditional purchase obligation receivable.

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Recorded unconditional purchase obligation receivable after fifth year.

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- Definition

Recorded unconditional purchase obligation receivable in fifth year.

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Recorded unconditional purchase obligation receivable in fourth year.

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- Definition

Recorded unconditional purchase obligation receivable in remainder of fiscal year.

+ References

No definition available.

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- Definition

Recorded unconditional purchase obligation receivable in second year.

+ References

No definition available.

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- Definition

Recorded unconditional purchase obligation receivable in third year.

+ References

No definition available.

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- Definition

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 440
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121559207&loc=d3e25383-109308

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- Definition

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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- Definition

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

+ References

No definition available.

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- Definition

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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- Definition

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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