Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,336.0	$ 1,545.3	$ 1,209.3
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Gains (Losses) on Available for Sale Debt Securities	(1,474.7)	(534.7)	527.8
Net Unrealized Gains (Losses) on Cash Flow Hedges	3.6	0.8	0.5
Net Foreign Currency Adjustments	9.4	10.5	26.9
Net Pension and Other Postretirement Benefit Adjustments	(71.9)	59.8	67.5
Other Comprehensive Income (Loss)	(1,533.6)	(463.6)	622.7
Comprehensive Income (Loss)	$ (197.6)	$ 1,081.7	$ 1,832.0