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Summary of Significant Accounting Policies - Revenue Recognition and Allowances for Accounts Receivable and Unbilled Services (Details) - USD ($) $ in Thousands | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Jan. 02, 2021 | Dec. 28, 2019 | Dec. 29, 2018 | Dec. 30, 2017
Revenue Recognition |  |  |  |
Cumulative effect of a change in accounting principle | $ 209,019 | $ 197,751 | $ 196,472 | $ 207,229
Retained Earnings |  |  |  |
Revenue Recognition |  |  |  |
Cumulative effect of a change in accounting principle | $ 216,999 | 200,249 | $ 186,229 | 169,390
Cumulative Effect Period of Adoption, Adjustment | ASC 606 |  |  |  |
Revenue Recognition |  |  |  |
Cumulative effect of a change in accounting principle |  |  |  | 366
Cumulative Effect Period of Adoption, Adjustment | ASC 606 | Retained Earnings |  |  |  |
Revenue Recognition |  |  |  |
Cumulative effect of a change in accounting principle |  |  |  | $ 366
Cumulative Effect Period of Adoption, Adjustment | ASC 326 |  |  |  |
Revenue Recognition |  |  |  |
Cumulative effect of a change in accounting principle |  | (203) |  |
Cumulative Effect Period of Adoption, Adjustment | ASC 326 | Retained Earnings |  |  |  |
Revenue Recognition |  |  |  |
Cumulative effect of a change in accounting principle |  | $ (203) |  |
Minimum |  |  |  |
Revenue Recognition |  |  |  |
Period in which engagements are generally completed (months) | 3 months |  |  |
Maximum |  |  |  |
Revenue Recognition |  |  |  |
Period in which engagements are generally completed (months) | 6 months |  |  |

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