Stock-based Compensation (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2022	Jun. 30, 2021
Restricted Stock Units (RSUs)
Share-based Payment activity [Roll Forward]
Unvested at beginning of period (in shares)	786,800	912,400		940,300	1,096,200		912,400	1,096,200
Granted (in shares)	188,500			200,500			188,500	257,100
Vested (in shares)	(28,600)			(10,700)			(151,400)	(218,100)
Forfeited (in shares)	(7,700)			(12,000.0)			(10,500)	(17,100)
Unvested at end of period (in shares)	939,000.0	786,800	912,400	1,118,100	940,300	1,096,200	939,000.0	1,118,100
Performance Shares [Member]
Share-based Payment activity [Roll Forward]
Unvested at beginning of period (in shares)	466,100	646,000.0		439,100	531,500		646,000.0	531,500
Granted (in shares)	113,000.0			107,200			113,000.0	107,200
Vested (in shares)	0			0			(175,100)	(79,000.0)
Forfeited (in shares)	(2,200)			(1,100)			(7,000.0)	(14,500)
Unvested at end of period (in shares)	576,900	466,100	646,000.0	545,200	439,100	531,500	576,900	545,200
Share-based Payment Arrangement [Member]
Share-based Payment activity [Roll Forward]
Unvested at beginning of period (in shares)	1,252,900	1,558,400		1,379,400	1,627,700		1,558,400	1,627,700
Granted (in shares)	301,500			307,700			301,500	364,300
Vested (in shares)	(28,600)			(10,700)			(326,500)	(297,100)
Forfeited (in shares)	(9,900)			(13,100)			(17,500)	(31,600)
Unvested at end of period (in shares)	1,515,900	1,252,900	1,558,400	1,663,300	1,379,400	1,627,700	1,515,900	1,663,300
Share-based Payment activity, additional disclosures [Abstract]
Weighted average grant date fair value, beginning of period (in dollars per share)	$ 152.62	$ 152.27		$ 134.84	$ 137.42		$ 152.27	$ 137.42
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	224.59			186.21			223.61	179.95
Weighted average grant date fair value, vested (in dollars per share)	129.96			142.07			147.57	150.45
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value	173.02			123.85			173.44	138.47
Weighted average grant date fair value, end of period (in dollars per share)	$ 167.23	$ 152.62	$ 152.27	$ 144.01	$ 134.84	$ 137.42	$ 167.23	$ 144.01
Weighted average remaining contractual life, unvested shares outstanding	1 year 11 months 23 days	1 year 10 months 2 days	1 year 11 months 26 days	1 year 11 months 1 day	1 year 8 months 12 days	1 year 8 months 8 days	1 year 11 months 23 days	1 year 11 months 1 day
Unamortized deferred compensation cost	$ 121.8						$ 121.8

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

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Weighted average remaining contractual term for equity-based awards excluding options, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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