Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flow from operating activities:
Net income	$ 608.6	$ 649.0	$ 800.6
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	670.4	671.6	667.4
Equity in earnings of unconsolidated affiliates, net	(100.0)	(25.8)	(25.4)
Distributions received from unconsolidated affiliates	21.2	2.3	10.0
Gain on bargain purchase	0.0	0.0	(2.6)
Stock-based compensation expense	159.5	124.8	114.0
Net gains on investments	(2.2)	(26.1)	(19.0)
Amortization and write-offs of loan origination costs and original issue discounts	13.5	13.9	13.2
Loss on extinguishment of debt, net	2.1	5.5	10.9
Loss on sale or disposition of property and equipment	11.7	0.6	1.0
Deferred income taxes	(82.9)	(77.0)	(88.0)
Provision for credit losses	11.4	10.6	8.2
Changes in operating assets and liabilities, excluding effects from acquisitions:
Accounts receivable	(23.1)	(38.1)	(72.2)
Prepaid expenses and other assets	(2.3)	17.7	49.5
Contract assets	22.5	(52.1)	(4.0)
Accounts payable	33.0	7.6	0.6
Accrued expenses and other liabilities	(106.0)	(135.5)	2.4
Income taxes prepaid and payable	(38.2)	27.0	2.6
Deferred revenue	15.9	(41.7)	(40.2)
Net cash provided by operating activities	1,215.1	1,134.3	1,429.0
Cash flow from investing activities:
Cash paid for asset acquisitions and business acquisitions, net of cash acquired	(34.1)	(1,636.2)	7.3
Additions to property and equipment	(56.6)	(63.4)	(51.3)
Proceeds from sale of property and equipment	0.1	11.4	5.3
Additions to capitalized software	(194.9)	(144.9)	(85.3)
Investments in securities	(0.6)	(10.0)	(20.1)
Proceeds from sales / maturities of investments	8.0	9.5	50.9
(Contributions to) distributions received from unconsolidated affiliates	(0.3)	66.2	(66.0)
Collection of other non-current receivables	10.0	9.8	11.0
Net cash used in investing activities	(268.4)	(1,757.6)	(148.2)
Cash flow from financing activities:
Cash received from debt borrowings, net of original issue discount	375.0	1,727.1	370.0
Repayments of debt	(749.7)	(599.8)	(889.9)
Payment of deferred financing fees	0.0	(14.7)	0.0
Net increase (decrease) in client funds obligations	1,669.7	(1,709.0)	1,480.5
Proceeds from exercise of stock options	115.4	91.8	197.7	$ 197.7
Withholding taxes paid related to equity award net share settlement	(5.1)	(0.7)	(7.0)
Purchases of common stock for treasury	(471.6)	(476.1)	(487.9)
Dividends paid on common stock	(220.9)	(203.1)	(174.0)
Proceeds from noncontrolling interests	0.0	0.0	67.3
Net provided by (used in) financing activities	712.8	(1,184.5)	556.7
Effect of exchange rate changes on cash, cash equivalents and restricted cash	1.5	(26.0)	(4.0)
Net increase (decrease) in cash, cash equivalents and restricted cash	1,661.0	(1,833.8)	1,833.5
Cash, cash equivalents and restricted cash, beginning of period	1,337.6	3,171.4	1,337.9
Cash, cash equivalents and restricted cash and cash equivalents, end of period	2,998.6	1,337.6	3,171.4	$ 1,337.9
Reconciliation of cash, cash equivalents and restricted cash and cash equivalents:
Cash and cash equivalents	432.2	440.1	564.0
Restricted cash and cash equivalents	2.4	3.3	4.2
Restricted cash and cash equivalents included in funds receivable and funds held on behalf of clients	2,564.0	894.2	2,603.2
Cash and cash equivalents and restricted cash	2,998.6	1,337.6	3,171.4
Supplemental disclosure of cash paid for:
Interest	461.8	298.0	192.5
Income taxes, net of refunds	$ 348.5	$ 281.1	$ 310.4