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Restricted Stock, Performance Share and Cash Awards - Additional Information (Detail) $ in Millions				3 Months Ended				9 Months Ended
	Mar. 15, 2023 USD ($) shares	May 10, 2022 shares	Mar. 15, 2022 USD ($) shares	Sep. 30, 2023 USD ($) shares	Mar. 31, 2023 USD ($) shares	Sep. 30, 2022 USD ($) shares	Mar. 31, 2022 USD ($) shares	Sep. 30, 2023 USD ($) TIME shares	Sep. 30, 2022 USD ($) shares	Dec. 31, 2022 shares	Mar. 31, 2021 shares	Mar. 16, 2021 USD ($) shares	Mar. 12, 2020 USD ($) shares
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Share-based compensation, shares outstanding | shares				8,200,000				8,200,000		8,300,000
Officer and Key Employees [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Performance awards period, years								1 year
Restricted Stock Units (RSUs) [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Period of service from grant date stock options awarded not subject to forfeiture					2 years		2 years
Restricted stock or unit expense				$ 11.4		$ 9.3		$ 32.1	$ 27.0
Restricted Stock Units (RSUs) [Member] | Executive Officer [Member] | Minimum [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Minimum age of employee with not subject to award forfeiture on condition compliance					55 years		55 years
Restricted Stock Units (RSUs) [Member] | Tranche One [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Shares granted in the period | shares					378,000		295,000
Fair value of grants in period					$ 67.0		$ 46.8
Share based payment award vesting date					Mar. 15, 2028		Mar. 15, 2027
Restricted Stock Units (RSUs) [Member] | Tranche Two [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Shares granted in the period | shares							335,000
Fair value of grants in period							$ 52.6
Share based payment award vesting date							Feb. 01, 2027
Unvested Restricted Stock [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Total intrinsic value				478.6		366.8		478.6	366.8
Equity awards with an aggregate fair value								62.0	62.0
Performance Shares [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Restricted stock or unit expense				5.5		3.8		14.0	11.3
Total intrinsic value				74.1		57.0		74.1	57.0
Equity awards with an aggregate fair value								$ 28.9	21.8
Performance share awards approved, Fair value	$ 10.3		$ 8.6
Vesting period, years					2 years
2017 Performance Share Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional awards, terms								The 2023 and 2022 awards are subject to a three-year performance period that began on January 1, 2023 and 2022, respectively, and vest on the three-year anniversary of the date of grant (March 15, 2026 and March 15, 2025).
Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Shares granted in the period | shares								0
Cash Awards [Member] | Officer and Key Employees [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional awards, terms								The ultimate award value will be equal to the trailing twelve-month price of our common stock, multiplied by the number of units subject to the award, but limited to between 0.5 and 1.5 times the original value of the units determined as of the grant date.
Vesting period, years								3 years
Provisional compensation cash awards approved for future grant by compensation committee, value			$ 19.9									$ 18.8
Provisional compensation cash award approved for future grant by compensation committee, units | shares			125,000				143,000				208,000	147,000
Ultimate award value, multiples of original value of the units, minimum | TIME								0.5
Ultimate award value, multiples of original value of the units, maximum | TIME								1.5
2023 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Cash-based compensation awards, expenses				3.7				$ 9.4
2021 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Cash-based compensation awards, expenses				$ 3.3		3.4		$ 9.8	8.9
Performance awards expiration date								Jan. 01, 2024
2020 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional compensation cash award approved for future grant by compensation committee, units | shares				191,000				191,000
Cash-based compensation awards, expenses						$ 3.0		$ 0.1	$ 9.0
Cash award with aggregate fair value vested and distributed to participants								$ 24.7
Performance awards expiration date								Jan. 01, 2023
2019 Provisional Cash Awards [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional compensation cash award approved for future grant by compensation committee, units | shares						177,000			177,000
Cash award with aggregate fair value vested and distributed to participants									$ 21.1
2019 Provisional Cash Awards [Member] | Officer and Key Employees [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Provisional compensation cash awards approved for future grant by compensation committee, value													$ 18.4
Provisional compensation cash award approved for future grant by compensation committee, units | shares													213,000
Long Term Incentive Plan [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Share-based compensation, shares outstanding, Value				$ 4.0				$ 4.0
Shares granted in the period | shares		3,500,000						2,800,000
Long Term Incentive Plan [Member] | Performance Shares [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Shares authorized | shares	58,000
2017 Long Term Incentive Plan [Member] | Minimum [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Period of service from grant date stock options awarded not subject to forfeiture								2 years	2 years
2017 Long Term Incentive Plan [Member] | Executive Officer [Member] | Minimum [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Minimum age of employee with not subject to award forfeiture on condition compliance								55 years	55 years
2017 Long Term Incentive Plan [Member] | Performance Shares [Member]
Common Stock Options Restricted Stock Warrants And Changes In Capitalization [Line Items]
Shares authorized | shares			54,000

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