Income Taxes - Income Taxes (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Federal Rate	21.00%	21.00%	35.00%
Tax at Statutory Rate	$ 408.3	$ 411.1	$ 571.9
Tax Exempt Income	(11.5)	(6.9)	(9.6)
Foreign Tax Rate Differential	4.6	(7.3)	(50.0)
Excess Tax Benefit Related to Share-Based Compensation	(17.5)	(16.8)	(31.6)
State Taxes, net	55.0	66.3	40.7
Impact of Tax Cuts and Jobs Act	0.0	(4.8)	(53.1)
Change in Accounting Method	0.0	(24.4)	0.0
Valuation Allowance	29.5	(0.8)	0.3
Other	(16.5)	(15.0)	(33.7)
Provision for Income Taxes	$ 451.9	$ 401.4	$ 434.9