Schedule I - Condensed Financial Information of the Registrant - Condensed Statements of Cash Flow (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities
Net cash provided by/(used in) operating activities	$ 1,045.3	$ 877.5	$ 914.6
Cash flows from investing activities
Purchases of property and equipment and other	(37.7)	(36.5)	(48.1)
Proceeds from the sale of former corporate headquarters (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 4)			711.7
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
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)
Proceeds from exercise of options and other	11.6	2.2	36.7
Cash dividends and dividend equivalents paid	(381.6)	(370.3)	(340.8)
Common stock repurchased	(409.9)	(239.7)	(552.6)
Make-whole premium on early extinguishment of debt	(14.3)
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)
Supplemental cash flow information:
Cash paid for lease liabilities	46.5	65.9	53.8
Non-cash lease liabilities arising from obtaining right-of-use assets (Note 6)	18.5	38.6	269.1
Parent Company | Reportable Legal Entities
Cash flows from operating activities
Net cash provided by/(used in) operating activities	510.4	(79.0)	103.1
Cash flows from investing activities
Purchases of property and equipment and other	(0.5)	(1.0)	(9.9)
Proceeds from the sale of former corporate headquarters (Note 4)		43.6
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 4)			711.7
Distributions received from/(capital contributed to) subsidiaries, net	6.5	(329.4)	74.0
Other investing activities	0.5	(2.1)
Net cash (used in)/provided by investing activities	57.4	(288.9)	775.8
Cash flows from financing activities
Advances from subsidiaries, net	289.5	1,139.5	194.0
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)
Proceeds from exercise of options and other	11.6	2.2	33.3
Cash dividends and dividend equivalents paid	(381.6)	(370.3)	(340.8)
Common stock repurchased	(409.9)	(239.7)	(552.6)
Make-whole premium on early extinguishment of debt	(14.3)
Other financing activities	0.2	(0.7)
Net cash used in financing activities	(567.8)	366.0	(875.1)
Net change in cash and cash equivalents, including settlement, and restricted cash		(1.9)	3.8
Cash and cash equivalents, including settlement, and restricted cash at beginning of period	2.1	4.0	0.2
Cash and cash equivalents, including settlement, and restricted cash at end of period	2.1	2.1	4.0
Supplemental cash flow information:
Non-cash financing activity, distribution of note from subsidiary (Note 3)	556.1	1,364.4
Cash paid for lease liabilities	14.6	20.7	17.0
Non-cash lease liabilities arising from obtaining right-of-use assets (Note 6)	$ 0.9	$ 1.5	$ 124.8