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Credit and Other Debt Agreements - Credit Agreement - Additional Information (Detail) $ in Millions, $ in Millions, $ in Millions |  | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Jun. 22, 2023 USD ($) | Dec. 31, 2023 AUD ($) | Dec. 31, 2023 NZD ($) | Dec. 31, 2023 USD ($) | Dec. 31, 2023 AUD ($) | Dec. 31, 2023 NZD ($) | Nov. 07, 2023 USD ($) | Dec. 31, 2022 USD ($)
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Total liabilities |  |  |  | $ 40,800.5 |  |  |  | $ 29,168.2
Long-term debt |  |  |  | 23.6 |  |  |  |
Revolving Credit Facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Credit facility, term | 5 years |  |  |  |  |  |  |
Line of Credit Facility, Current Borrowing Capacity | $ 1,200.0 |  |  |  |  |  | $ 1,700.0 |
Line of credit facility, amount outstanding |  |  |  | 289.0 |  |  |  |
Interest rate for facility |  | The interest rates on Facility B are Interbank rates, which vary by tranche, duration and currency, plus a margin of 1.500% and 1.850% for the AU$ and NZ$ tranches, respectively. The interest rates on Facilities C and D are 30 day Interbank rates, plus a margin of 0.830% and 0.990% for the AU$ and NZ$ tranches, respectively. The annual fee for Facility B is 0.675% and 0.8325% for the undrawn commitments for the AU$ and NZ$ tranches, respectively. The annual fee for Facility C is 0.77% and for Facility D is 0.90% of the total commitments of the facilities | The interest rates on Facility B are Interbank rates, which vary by tranche, duration and currency, plus a margin of 1.500% and 1.850% for the AU$ and NZ$ tranches, respectively. The interest rates on Facilities C and D are 30 day Interbank rates, plus a margin of 0.830% and 0.990% for the AU$ and NZ$ tranches, respectively. The annual fee for Facility B is 0.675% and 0.8325% for the undrawn commitments for the AU$ and NZ$ tranches, respectively. The annual fee for Facility C is 0.77% and for Facility D is 0.90% of the total commitments of the facilities |  |  |  |  |
Debt instrument fair value amount |  |  |  | 289.0 |  |  |  |
Letter of Credit Sub-facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of Credit Facility, Current Borrowing Capacity | $ 75.0 |  |  |  |  |  |  |
Credit Facility Two [Member] | Revolving Credit Facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of credit facility, amount outstanding |  |  |  |  | $ 365.0 | $ 0.0 |  |
Line of credit facility, remaining borrowing capacity |  |  |  |  | 25.0 | 25.0 |  |
Net borrowings on premium financing debt facility |  | $ 390.0 | $ 25.0 |  |  |  |  |
Credit Facility Three [Member] | Revolving Credit Facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of credit facility, amount outstanding |  |  |  |  | 45.9 |  |  |
Line of credit facility, remaining borrowing capacity |  |  |  |  | $ 14.1 |  |  |
Net borrowings on premium financing debt facility |  | $ 60.0 | $ 10.0 |  |  |  |  |
Annual fee percentage |  | 0.77% | 0.77% |  |  |  |  |
Credit Facility Four [Member] | Revolving Credit Facility [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of credit facility, amount outstanding |  |  |  |  |  | 13.7 |  |
Line of credit facility, remaining borrowing capacity |  |  |  |  |  | $ 1.3 |  |
Net borrowings on premium financing debt facility |  |  | $ 15.0 |  |  |  |  |
Annual fee percentage |  | 0.90% | 0.90% |  |  |  |  |
AUD Denominated Tranche [Member] | Revolving Credit Facility [Member] | Facility B [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Additional margin percentage on interest rate |  | 1.50% | 1.50% |  |  |  |  |
Annual fee percentage |  | 0.675% | 0.675% |  |  |  |  |
AUD Denominated Tranche [Member] | Revolving Credit Facility [Member] | Facility C and D [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Additional margin percentage on interest rate |  | 0.83% | 0.83% |  |  |  |  |
NZD Denominated Tranche [Member] | Revolving Credit Facility [Member] | Facility B [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Additional margin percentage on interest rate |  | 1.85% | 1.85% |  |  |  |  |
Annual fee percentage |  | 0.8325% | 0.8325% |  |  |  |  |
NZD Denominated Tranche [Member] | Revolving Credit Facility [Member] | Facility C and D [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Additional margin percentage on interest rate |  | 0.99% | 0.99% |  |  |  |  |
Note Purchase Agreements [Member] | Level 3 [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of credit facility, fair value of amount outstanding |  |  |  | 6,840.2 |  |  |  |
Long-term debt |  |  |  | 7,498.0 |  |  |  |
Unsecured Multicurrency Credit Agreement [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Estimated fair value of outstanding borrowings |  |  |  | 245.0 |  |  |  |
Unsecured Multicurrency Credit Agreement [Member] | Standby Letters of Credit [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Line of credit facility, maximum borrowing capacity |  |  |  | 1,443.4 |  |  |  |
Line of credit facility, amount outstanding |  |  |  | 11.6 |  |  |  |
Total liabilities |  |  |  | 13.7 |  |  |  |
Line of credit facility, fair value of amount outstanding |  |  |  | $ 245.0 |  |  |  |
Unsecured Multicurrency Credit Agreement [Member] | Minimum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rates on base rate loans |  | 0.00% | 0.00% |  |  |  |  |
Fixed rate over SOFR rate, eurocurrency rate or RFR rate |  | 0.775% | 0.775% |  |  |  |  |
Annual facility fee of revolving credit facility |  | 0.10% | 0.10% |  |  |  |  |
Unsecured Multicurrency Credit Agreement [Member] | Maximum [Member] |  |  |  |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |  |  |  |
Interest rates on base rate loans |  | 0.375% | 0.375% |  |  |  |  |
Fixed rate over SOFR rate, eurocurrency rate or RFR rate |  | 1.375% | 1.375% |  |  |  |  |
Annual facility fee of revolving credit facility |  | 0.25% | 0.25% |  |  |  |  |

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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. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -SubTopic 10 -Topic 210 -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(16)(a)(2)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479440/944-210-S99-1 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Topic 942 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147479853/942-210-S99-1 + Details
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- Definition Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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- Definition Fair value of the amount outstanding under the credit facility. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 825 -SubTopic 10 -Name Accounting Standards Codification -Section 50 -Paragraph 10 -Publisher FASB -URI https://asc.fasb.org//1943274/2147482907/825-10-50-10 + Details
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- Definition Description of interest rate for borrowing under credit facility. Includes, but is not limited to, terms and method for determining interest rate. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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- Definition Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -Publisher FASB -URI https://asc.fasb.org//1943274/2147480566/210-10-S99-1 + Details
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