Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net Income	$ 395.7	$ 294.5	$ 1,138.9	$ 968.4
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Gains (Losses) on Available for Sale Debt Securities	(89.6)	33.5	(358.4)	551.3
Net Unrealized Gains (Losses) on Cash Flow Hedges	4.6	1.3	2.4	5.3
Net Foreign Currency Adjustments	3.8	1.8	10.9	29.5
Net Pension and Other Postretirement Benefit Adjustments	0.5	17.5	31.1	33.1
Net Change	(80.7)	54.1	(314.0)	619.2
Comprehensive Income	$ 315.0	$ 348.6	$ 824.9	$ 1,587.6