CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,736.9	$ 2,031.1	$ 1,107.3
Other Comprehensive Income (Net of Tax and Reclassifications)
Net Unrealized Gains on Available for Sale Debt Securities	196.8	325.8	443.7
Net Unrealized Gains (Losses) on Cash Flow Hedges	0.3	(0.2)	(0.4)
Net Foreign Currency Adjustments	15.8	29.5	39.0
Net Pension and Other Postretirement Benefit Adjustments	10.6	(31.2)	(51.0)
Net Change	223.5	323.9	431.3
Comprehensive Income	$ 1,960.4	$ 2,355.0	$ 1,538.6