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v3.20.4

Other Financial Data - Schedule of Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Jan. 01, 2020 | Dec. 31, 2017
Accounts Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |  |
Balance at beginning of period | $ 70 | $ 62 | $ 59 |  |
Provision | 29 | 27 | 24 |  |
Accounts written off, net of recoveries | (6) | (19) | (25) |  |
Foreign currency translation and other | (2) | 0 | 4 |  |
Balance at end of period | 98 | 70 | 62 |  |
Cumulative adjustment amount to decrease retained earnings | (3,583) | (3,449) | (4,219) |  | $ (4,648)
Retained Earnings |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |  |
Cumulative adjustment amount to decrease retained earnings | (1,042) | (1,254) | (2,093) |  | (2,302)
Cumulative Effect, Period of Adoption, Adjustment |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |  |
Balance at beginning of period | 7 | 0 | 0 |  |
Balance at end of period |  | 7 | 0 |  |
Cumulative adjustment amount to decrease retained earnings |  | 6 |  |  | (492)
Cumulative Effect, Period of Adoption, Adjustment | Retained Earnings |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |  |
Cumulative adjustment amount to decrease retained earnings |  | 6 |  | $ 6 | (493)
Cumulative Effect, Period of Adoption, Adjusted Balance |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |  |
Balance at beginning of period | $ 77 | 62 | 59 |  |
Balance at end of period |  | 77 | $ 62 |  |
Cumulative adjustment amount to decrease retained earnings |  | (3,443) |  |  | (5,140)
Cumulative Effect, Period of Adoption, Adjusted Balance | Retained Earnings |  |  |  |  |
Accounts Receivable, Allowance for Credit Loss [Roll Forward] |  |  |  |  |
Cumulative adjustment amount to decrease retained earnings |  | $ (1,248) |  |  | $ (2,795)

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