Consolidated Balance Sheet - USD ($) $ in Millions	Jun. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Cash and cash equivalents	$ 1,415.3	$ 971.5
Fiduciary assets (includes fiduciary cash of $5,422.5 and $5,571.8 in 2023)	37,316.9	26,907.9
Accounts receivable, net	4,178.3	3,786.6
Other current assets	403.0	450.1
Total current assets	43,313.5	32,116.1
Fixed assets - net	655.3	726.4
Deferred income taxes (includes tax credit carryforwards of $805.1 in 2024 and $867.4 in 2023)	1,040.1	1,132.3
Other noncurrent assets	1,311.6	1,131.8
Right-of-use assets	382.3	400.3
Goodwill	11,915.5	11,475.6
Amortizable intangible assets - net	4,389.4	4,633.3
Total assets	63,007.7	51,615.8
Fiduciary liabilities	37,316.9	26,907.9
Accrued compensation and other current liabilities	3,107.8	2,553.1
Deferred revenue - current	697.1	644.7
Premium financing debt	207.8	289.0
Corporate related borrowings - current	280.0	670.0
Total current liabilities	41,609.6	31,064.7
Corporate related borrowings - noncurrent	7,790.9	7,006.0
Deferred revenue - noncurrent	65.8	61.5
Lease liabilities - noncurrent	335.2	352.2
Other noncurrent liabilities	1,606.9	2,316.1
Total liabilities	51,408.4	40,800.5
Stockholders' equity:
Common stock - issued and outstanding 219.1 shares in 2024 and 216.7 shares in 2023	219.1	216.7
Capital in excess of par value	7,611.4	7,297.8
Retained earnings	4,681.2	4,052.9
Accumulated other comprehensive loss	(939.2)	(792.1)
Stockholders' equity attributable to controlling interests	11,572.5	10,775.3
Stockholders' equity attributable to noncontrolling interests	26.8	40.0
Total stockholders' equity	11,599.3	10,815.3
Total liabilities and stockholders' equity	$ 63,007.7	$ 51,615.8