Fair Value Measurements (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Trading Securities at Fair Value	$ 98.6	$ 82.6
Investments, Fair Value Disclosure	41.4
Fair Value, Measurements, Recurring [Member]
Investments, Fair Value Disclosure	115.0	100.9
Total Assets at Fair Value	115.0	100.9
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Investments, Fair Value Disclosure	115.0	100.6
Total Assets at Fair Value	115.0	100.6
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Investments, Fair Value Disclosure	0.0	0.3
Total Assets at Fair Value	0.0	0.3
Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Investments, Fair Value Disclosure	0.0	0.0
Total Assets at Fair Value	0.0	0.0
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Marketable Securities	16.2	17.9
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Marketable Securities	16.2	17.9
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Marketable Securities	0.0	0.0
Corporate Debt Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Marketable Securities	0.0	0.0
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member]
Trading Securities at Fair Value	98.6	82.6
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Trading Securities at Fair Value	98.6	82.6
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Trading Securities at Fair Value	0.0	0.0
Mutual Fund [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Trading Securities at Fair Value	0.0	0.0
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Marketable Securities	0.2	0.1
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Marketable Securities	0.2	0.1
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Marketable Securities	0.0	0.0
Equity Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Marketable Securities	$ 0.0	0.0
Asset-backed Securities [Member] \| Fair Value, Measurements, Recurring [Member]
Marketable Securities		0.3
Asset-backed Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 1 [Member]
Marketable Securities		0.0
Asset-backed Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 2 [Member]
Marketable Securities		0.3
Asset-backed Securities [Member] \| Fair Value, Measurements, Recurring [Member] \| Fair Value, Inputs, level 3 [Member]
Marketable Securities		$ 0.0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_AssetsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

Name:	us-gaap_InvestmentsFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in marketable security.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878

+ Details

Name:	us-gaap_MarketableSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

+ Details

Name:	us-gaap_TradingSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_CorporateDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_MutualFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: