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Schedule II: Valuation and Qualifying Accounts Schedule II: Valuation and Qualifying Accounts (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
SEC Schedule, 12-09, Allowance, Credit Loss [Member] |  |  |
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] |  |  |
Balance at Beginning of Period | $ 583 | $ 455 | $ 763
Additions/Charged to Expense | 7,514 | 7,572 | 7,682
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction | 7,339 | 7,444 | 7,990
Balance at End of Period | 758 | 583 | 455
Allowance For Contract With Customer [Member] |  |  |
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] |  |  |
Balance at Beginning of Period | 159 | 162 | 195
Additions/Charged to Expense | 121 | 85 | 23
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction | 143 | 88 | 56
Balance at End of Period | 137 | 159 | 162
SEC Schedule, 12-09, Valuation Allowance, Deferred Tax Asset [Member] |  |  |
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward] |  |  |
Balance at Beginning of Period | 331 | 162 | 126
Additions/Charged to Expense | 3 | 170 | 72
SEC Schedule, 12-09, Valuation Allowances and Reserves, Deduction | 117 | 1 | 36
Balance at End of Period | $ 217 | $ 331 | $ 162

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