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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 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 + Details
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