Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,545.3	$ 1,209.3	$ 1,492.2
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Gains (Losses) on Available for Sale Debt Securities	(534.7)	527.8	228.9
Net Unrealized Gains (Losses) on Cash Flow Hedges	0.8	0.5	(7.7)
Net Foreign Currency Adjustments	10.5	26.9	49.9
Net Pension and Other Postretirement Benefit Adjustments	59.8	67.5	(12.1)
Other Comprehensive Income (Loss)	(463.6)	622.7	259.0
Comprehensive Income	$ 1,081.7	$ 1,832.0	$ 1,751.2