Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net Income	$ 389.3	$ 375.1
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Losses on Available for Sale Debt Securities	(868.4)	(369.7)
Net Unrealized Losses on Cash Flow Hedges	(1.4)	(5.2)
Net Foreign Currency Adjustments	(7.9)	5.0
Net Pension and Other Postretirement Benefit Adjustments	6.3	7.8
Net Change	(871.4)	(362.1)
Comprehensive Income (Loss)	$ (482.1)	$ 13.0