Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net Income	$ 1,209.3	$ 1,492.2	$ 1,556.4
Other Comprehensive Income (Loss) (Net of Tax and Reclassifications)
Net Unrealized Gains on Debt Securities Available for Sale	527.8	228.9	(22.3)
Net Unrealized Gains (Losses) on Cash Flow Hedges	0.5	(7.7)	(1.4)
Net Foreign Currency Adjustments	26.9	49.9	22.2
Net Pension and Other Postretirement Benefit Adjustments	67.5	(12.1)	(12.6)
Other Comprehensive Income	622.7	259.0	(14.1)
Comprehensive Income	$ 1,832.0	$ 1,751.2	$ 1,542.3