AOCI Attributable To Parent, After Tax [Abstract]

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AOCI Attributable To Parent, Before Tax [Abstract]

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AOCI Attributable To Parent, Tax [Abstract]

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Amount before tax and reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

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-Name Accounting Standards Codification
-Topic 220
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Amount of tax expense (benefit) allocated to other comprehensive income (loss) before reclassification adjustment from accumulated other comprehensive income (loss).

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Amount before tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount of tax expense (benefit) allocated to other comprehensive income (loss) attributable to parent entity.

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Amount before tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Amount after tax of reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Amount of tax expense (benefit) of reclassification adjustment from accumulated other comprehensive income (loss).

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Accumulated Other Comprehensive Income (Loss) (Details of Changes In Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2025	Jun. 30, 2025	Mar. 31, 2025	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2025	Sep. 30, 2024
PRE-TAX
Net Change	$ 101.6			$ 80.4			$ 168.5	$ 468.9
TAX
Net Change	(37.5)			5.1			10.4	(110.5)
AFTER TAX
Other Comprehensive Income	64.1	$ 40.3	$ 74.5	85.5	$ 52.6	$ 220.3	178.9	358.4
Unrealized Gains (Losses) on Available for Sale Debt Securities
PRE-TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	33.6			63.7			142.7	176.9
Net Change	57.7			88.6			217.3	442.7
TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	(7.5)			(18.6)			(37.8)	(55.1)
Net Change	(13.4)			(24.7)			(56.1)	(122.0)
AFTER TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	26.1			45.1			104.9	121.8
Other Comprehensive Income	44.3			63.9			161.2	320.7
Interest Income on Debt Securities
PRE-TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:	24.1			24.9			74.6	76.5
TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:	(5.9)			(6.1)			(18.3)	(19.0)
AFTER TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:	18.2			18.8			56.3	57.5
Net Losses on Debt Securities
PRE-TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:							0.0	189.3
TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:							0.0	(47.9)
AFTER TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:							0.0	141.4
Unrealized Gains (Losses) on Cash Flow Hedges
PRE-TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	0.1			1.0			13.1	6.4
Reclassification Adjustments for (Gains) Losses Included in Net Income:	(0.2)			(0.6)			(14.1)	(7.1)
Net Change	(0.1)			0.4			(1.0)	(0.7)
TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	0.0			(0.2)			(3.1)	(1.5)
Reclassification Adjustments for (Gains) Losses Included in Net Income:	0.1			0.1			3.5	1.7
Net Change	0.1			(0.1)			0.4	0.2
AFTER TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	0.1			0.8			10.0	4.9
Reclassification Adjustments for (Gains) Losses Included in Net Income:	(0.1)			(0.5)			(10.6)	(5.4)
Other Comprehensive Income	0.0			0.3			(0.6)	(0.5)
Foreign Currency Adjustments
PRE-TAX
Net Change	41.1			(11.7)			(53.3)	16.4
TAX
Net Change	(23.5)			30.6			67.9	14.1
AFTER TAX
Other Comprehensive Income	17.6			18.9			14.6	30.5
Foreign Currency Translation Adjustments
PRE-TAX
Net Change	(21.9)			122.9			275.5	52.5
TAX
Net Change	(8.0)			(2.4)			(12.9)	(1.2)
AFTER TAX
Other Comprehensive Income	(29.9)			120.5			262.6	51.3
Long-Term Intra-Entity Foreign Currency Transaction Gains (Losses)
PRE-TAX
Net Change	0.2			1.0			0.8	0.2
TAX
Net Change	(0.1)			(0.3)			(0.1)	(0.1)
AFTER TAX
Other Comprehensive Income	0.1			0.7			0.7	0.1
Net Investment Hedge Gains (Losses)
PRE-TAX
Net Change	62.8			(135.6)			(329.6)	(36.3)
TAX
Net Change	(15.4)			33.3			80.9	15.4
AFTER TAX
Other Comprehensive Income	47.4			(102.3)			(248.7)	(20.9)
Pension and Other Postretirement Benefit Adjustments
PRE-TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	(0.1)			(0.1)			(3.5)	0.9
Net Change	2.9			3.1			5.5	10.5
TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	0.0			0.0			0.3	(0.5)
Net Change	(0.7)			(0.7)			(1.8)	(2.8)
AFTER TAX
Unrealized Gains (Losses) on Available for Sale Debt Securities	(0.1)			(0.1)			(3.2)	0.4
Other Comprehensive Income	2.2			2.4			3.7	7.7
Amortization of Net Actuarial Loss
PRE-TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:	3.0			3.2			9.0	9.6
TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:	(0.7)			(0.7)			(2.1)	(2.3)
AFTER TAX
Reclassification Adjustments for (Gains) Losses Included in Net Income:	$ 2.3			$ 2.5			$ 6.9	$ 7.3