Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net Income	$ 912.8	$ 750.2	$ 2,651.2	$ 2,411.6
Other comprehensive income (loss), net of tax:
Net unrealized holding gains (losses) arising during the period	0.6	(0.4)	0.6	(0.1)
Income tax benefit (expense)	(0.2)	0.1	(0.2)	0.0
Amortization of net actuarial (gains) losses included in compensation and benefits expense	0.1	0.1	0.1	0.1
Investment securities, net	0.4	(0.3)	0.4	(0.1)
Net change in defined benefit plans arising during the period	0.0	0.0	(5.9)	(3.5)
Income tax benefit (expense)	0.0	(0.1)	1.5	0.8
Defined benefit plans, net	0.1	0.0	(4.3)	(2.6)
Reclassification of net unrealized (gains) losses to interest expense and other non-operating income (expense)	(0.9)	(0.8)	(2.7)	(2.7)
Income tax benefit (expense)	0.3	0.2	0.7	0.7
Derivative investments, net	(0.6)	(0.6)	(2.0)	(2.0)
Foreign currency translation adjustments	88.4	(16.2)	54.8	20.7
Income tax benefit (expense)	(4.2)	0.0	(4.2)	0.0
Foreign currency translation, net	84.2	(16.2)	50.6	20.7
Other comprehensive income (loss), net of tax	84.1	(17.1)	44.7	16.0
Comprehensive income	$ 996.9	$ 733.1	$ 2,695.9	$ 2,427.6