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Stock-Based Compensation - Stock-based Compensation Expense by Award Type and Expense Category (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Feb. 03, 2021
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)	$ 21.0	$ 19.4	$ 77.6	$ 81.7
Cost of services and product development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)	7.6	6.9	27.0	28.6
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)	13.4	12.5	50.6	53.1
Stock appreciation rights
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)	2.2	2.1	6.6	6.1
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)	18.6	17.1	70.4	75.0
Common stock equivalents
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)	0.2	0.2	0.6	0.6
Retirement eligible employees equity award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)	$ 5.4	$ 5.5	$ 32.7	38.3
Performance-based RSUs | Executive officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense (credit)				$ 6.5
Target performance percentage	50.00%		50.00%		95.00%

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- Definition

Share-Based Compensation Arrangement By Share-based Payment Award, Equity Instruments Other Than Options, Target Performance Percentage

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- Definition

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (h)(1)(i)
-URI https://asc.fasb.org/extlink&oid=128089324&loc=d3e5070-113901

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