CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net income	$ 805.8	$ 744.3	$ 1,058.3
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation	49.6	61.3	79.6
Amortization	158.6	164.3	178.1
Pension settlement charges (Note 12)	109.8
Gain on divestiture of businesses, excluding transaction costs (Note 5)			(532.1)
Gain on sale of noncontrolling interest in a private company (Note 5)	(47.9)
Deferred income tax provision/(benefit) (Note 11)	(2.6)	13.9	(24.5)
Other non-cash items, net	149.6	145.8	118.4
Increase/(decrease) in cash, excluding the effects of divestitures, resulting from changes in:
Other assets	(73.0)	(44.4)	7.5
Accounts payable and accrued liabilities	(24.8)	(96.6)	94.3
Income taxes payable (Note 11)	(56.2)	(94.4)	(36.8)
Other liabilities	(23.6)	(16.7)	(28.2)
Net cash provided by operating activities	1,045.3	877.5	914.6
Cash flows from investing activities
Payments for capitalized contract costs	(107.5)	(69.1)	(46.6)
Payments for internal use software	(69.4)	(51.2)	(33.0)
Purchases of property and equipment	(37.7)	(36.5)	(48.1)
Purchases of settlement investments	(433.0)	(6,421.1)	(5,866.1)
Proceeds from the sale of settlement investments	755.3	5,978.4	5,219.1
Maturities of settlement investments	229.7	182.6	181.7
Proceeds from the sale of former corporate headquarters and other property (Note 4)		49.4
Proceeds from the sale of noncontrolling interest in a private company (Note 4)	50.9
Proceeds from divestitures of businesses, net of cash divested (Note 5)			711.7
Purchase the noncontrolling interest in stc Bank (Note 5)	(200.0)
Other investing activities	3.7	(6.0)	48.3
Net cash (used in)/provided by investing activities	192.0	(373.5)	167.0
Cash flows from financing activities
Cash dividends and dividend equivalents paid	(381.6)	(370.3)	(340.8)
Common stock repurchased (Note 14)	(409.9)	(239.7)	(552.6)
Net proceeds from/(repayments of) commercial paper	195.0	(165.0)	120.0
Net proceeds from issuance of borrowings	891.7		495.9
Principal payments on borrowings	(1,150.0)		(824.9)
Make-whole premium on early extinguishment of debt (Note 16)	(14.3)
Proceeds from exercise of options	11.6	2.2	36.7
Net change in settlement obligations	(412.2)	587.6	(414.3)
Other financing activities	0.2	(0.7)	(4.1)
Net cash used in financing activities	(1,269.5)	(185.9)	(1,484.1)
Net change in cash and cash equivalents, including settlement, and restricted cash	(32.2)	318.1	(402.5)
Cash and cash equivalents, including settlement, and restricted cash at beginning of period	2,143.1	1,825.0	2,227.5
Cash and cash equivalents, including settlement, and restricted cash at end of period	2,110.9	2,143.1	1,825.0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents on balance sheet	1,208.3	1,428.2	1,450.5
Settlement cash and cash equivalents (Note 8)	835.5	695.7	368.2
Restricted cash in Other assets	29.4	19.2	6.3
Cash and cash equivalents included in Assets held for sale (Note 5)	37.7
Cash and cash equivalents, including settlement, and restricted cash	2,110.9	2,143.1	1,825.0
Supplemental cash flow information:
Interest paid	101.6	109.6	151.3
Income taxes paid	185.9	187.3	318.9
Cash paid for lease liabilities	46.5	65.9	53.8
Non-cash lease liabilities arising from obtaining right-of-use assets (Note 13)	18.5	38.6	269.1
Internal use software capitalized but not yet paid	$ 26.4	$ 0.2	$ 1.6