CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME Unaudited (Parentheticals) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Statement of Comprehensive Income [Abstract]
Unrealized gain on securities, income tax expense	$ 0.0	$ 0.0	$ 0.0	$ 0.1
Defined benefit pension and other postretirement benefit plans, income tax benefit	$ (0.3)	$ (0.1)	$ (0.2)	$ (0.1)

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
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Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 810
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Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
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