| Dec 31, 2020 | Dec 31, 2021 | Dec 31, 2022 | Dec 31, 2023 | Dec 31, 2024 |
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| Revenue | - | 1,554 | 3,132 | 3,410 | 2,332 |
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| Cost of services, exclusive of depreciation and amortization | - | 1,001 | 2,080 | 2,188 | 1,442 |
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| Depreciation and amortization | - | 21 | 56 | 82 | 96 |
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| Gross Profit | - | 532 | 996 | 1,140 | 794 |
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| Selling, general and administrative | - | 304 | 671 | 754 | 585 |
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| Depreciation and intangible amortization | - | 163 | 339 | 339 | 299 |
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| Total Operating expenses | - | 467 | 1,010 | 1,241 | 884 |
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| Operating Income (Loss) From Continuing Operations | -3,258,112 | 65 | -14 | -101 | -90 |
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| (Gain) Loss from change in fair value of financial instruments | - | 65 | -38 | 10 | -57 |
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| (Gain) Loss from change in fair value of tax receivable agreement | - | 37 | 41 | -118 | -34 |
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| Interest expense | - | - | - | - | 103 |
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| Other (income) expense, net | - | -3 | 16 | -6 | 22 |
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| Total Other (income) expense, net | - | -88 | -27 | -265 | -58 |
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| Income (Loss) From Continuing Operations Before Taxes | -2,408,845 | -23 | -41 | -366 | -148 |
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| Income tax expense (benefit) | 147,695 | 25 | 31 | -4 | -8 |
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| Net Income (Loss) From Continuing Operations | - | - | - | - | -140 |
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| Net Income (Loss) From Discontinued Operations, Net of Tax | - | - | - | - | -19 |
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| Net Income (Loss) | -2,556,540 | -48 | -72 | -362 | -159 |
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| Net Income (Loss) Attributable to Noncontrolling Interest | - | -13 | -10 | -17 | -2 |
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| Net Income (Loss) Attributable to Alight, Inc. | -2,556,540 | -35 | -62 | -345 | -157 |
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| Continuing operations, basic (in dollars per share) | - | - | - | - | -0.25 |
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| Continuing operations, diluted (in dollars per share) | - | - | - | - | -0.25 |
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| Discontinued operations, basic (in dollars per share) | - | - | - | - | -0.04 |
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| Discontinued operations, diluted (in dollars per share) | - | - | - | - | -0.04 |
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| Net income (loss), basic (in dollars per share) | - | -0.08 | -0.14 | -0.7 | -0.29 |
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| Net income (loss), diluted (in dollars per share) | - | -0.08 | -0.14 | -0.7 | -0.29 |
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| Net Income (Loss) | -2,556,540 | -48 | -72 | -362 | -159 |
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| Change in fair value of derivatives | - | 9 | 114 | -42 | -35 |
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| Foreign currency translation adjustments | - | - | -14 | 9 | 7 |
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| Total Other comprehensive income (loss), net of tax: | - | 9 | 100 | -33 | -28 |
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| Comprehensive Income (Loss) Before Noncontrolling Interests | - | -39 | 28 | -395 | -187 |
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| Comprehensive income (loss) attributable to noncontrolling interests | - | -12 | 3 | -26 | -6 |
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| Comprehensive Income (Loss) Attributable to Alight, Inc. | - | -27 | 25 | -369 | -181 |
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