Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Statement of Comprehensive Income [Abstract]
Net Income	$ 334.6	$ 389.3
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Gains (Losses) on Available for Sale Debt Securities	180.2	(868.4)
Net Unrealized Gains (Losses) on Cash Flow Hedges	(0.1)	(1.4)
Net Foreign Currency Adjustments	22.7	(7.9)
Net Pension and Other Postretirement Benefit Adjustments	0.2	6.3
Net Change	203.0	(871.4)
Comprehensive Income (Loss)	$ 537.6	$ (482.1)