Amount payable to redeem notes percent of principal amount following transaction termination event.

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- Definition

Debt Instrument Maturity Year

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Debt instrument redemption date.

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- Definition

Number of days to occur reinsurance transaction termination event for note redemption.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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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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Weighted average interest rate of debt outstanding.

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- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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No definition available.

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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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Reflects the difference between the fair value of payments made to legally extinguish a debt and its carrying value at that time. This item excludes the write-off of amounts previously capitalized as debt issuance costs.

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The fair value of notes issued in noncash investing and financing activities.

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The excess of the (1) fair value of consideration transferred to the holders of a security in excess of (2) the carrying amount of the security reported on the registrant's balance sheet, which will be deducted from net earnings to derive net earnings available to common shareholders. This amount is generally an adjustment considered in the computation of earnings per share.

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Credit and Other Debt Agreements - Senior Notes - Additional Information (Detail) - USD ($) $ in Millions			12 Months Ended
	Nov. 09, 2021	May 20, 2021	Dec. 31, 2021	Dec. 31, 2022
Debt Instrument [Line Items]
Loss on extinguishment of debt			$ 16.2
Fixed Rate of 3.50%, Balloon Due May 20, 2051 [Member]
Debt Instrument [Line Items]
Periodic payment of interest			3.50%	3.50%
Fixed Rate of 2.40%, Balloon Due November 9, 2031 [Member]
Debt Instrument [Line Items]
Periodic payment of interest			2.40%	2.40%
Fixed Rate of 3.05%, Balloon Due March 9, 2052 [Member]
Debt Instrument [Line Items]
Periodic payment of interest			3.05%	3.05%
Unsecured Senior Notes [Member]
Debt Instrument [Line Items]
Notes issued and sold	$ 750.0	$ 1,500.0
Weighted average interest rate	2.80%	3.31%
Realized a cash gain (loss) on hedging transaction		$ (57.8)
Derivative instrument, term		10 years
Unsecured Senior Notes [Member] \| Fixed Rate of 2.50%, Balloon Due May 20, 2031 [Member]
Debt Instrument [Line Items]
Notes issued and sold		$ 650.0
Periodic payment of interest		2.50%
Periodic payments of interest and principal, expiry year		2031
Amount payable to redeem the notes, percent of the principal amount following transaction termination event		101.00%
Number of days to occur reinsurance transaction termination event for note redemption		30 days
Notes redemption date		Aug. 13, 2021
Loss on extinguishment of debt		$ 16.2
Redemption premium		6.5
Unamortized discount amount debt issuance and write-off debt acquisition costs		9.7
Unsecured Senior Notes [Member] \| Fixed Rate of 3.50%, Balloon Due May 20, 2051 [Member]
Debt Instrument [Line Items]
Notes issued and sold		$ 850.0
Periodic payment of interest		3.50%
Periodic payments of interest and principal, expiry year		2051
Unsecured Senior Notes [Member] \| Fixed Rate of 2.40%, Balloon Due November 9, 2031 [Member]
Debt Instrument [Line Items]
Notes issued and sold	$ 400.0
Periodic payment of interest	2.40%
Periodic payments of interest and principal, expiry year	2031
Unsecured Senior Notes [Member] \| Fixed Rate of 3.05%, Balloon Due March 9, 2052 [Member]
Debt Instrument [Line Items]
Notes issued and sold	$ 350.0
Periodic payment of interest	3.05%
Periodic payments of interest and principal, expiry year	2052