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Income Taxes - Narrative (Details) - USD ($) $ in Millions |  | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | ---
Mar. 01, 2017 | Mar. 31, 2018 | Dec. 31, 2017 | Mar. 31, 2018 | Mar. 31, 2017 | Mar. 31, 2016 | Sep. 30, 2017 | Mar. 31, 2015
Income Tax Contingency [Line Items] |  |  |  |  |  |  |  |
Income tax expense |  |  |  | $ (53) | $ 1,614 | $ 908 |  |
Income tax rates (percent) |  |  |  | 22.20% | 23.40% | 27.90% |  |
Statutory federal income tax rate (percent) |  |  |  | 31.60% | 35.00% | 35.00% |  |
Research and development credit |  |  |  | $ 11 |  |  |  |
Transition tax on foreign earnings |  |  |  | 457 | $ 0 | $ 0 |  |
Goodwill impairment charge |  |  |  | 1,738 | 290 | 0 |  |
Net tax benefit on intellectual property transfer |  |  |  | 178 | 137 | 0 |  |
Tax expense recognized on gain from asset exchange | $ 929 |  |  |  |  |  |  |
Tax benefit related to adoption of amended accounting guidance |  |  |  | 8 | 54 | 0 |  |
Net discrete tax expense (benefit) |  |  |  |  |  | (19) |  |
Discrete tax benefit |  |  |  |  |  | 25 |  |
Valuation allowance |  | $ 751 |  | 751 | 503 |  |  |
Increase in valuation allowance |  |  |  | 248 |  |  |  |
Unrecognized tax benefits |  | 1,183 |  | 1,183 | 486 | 555 |  | $ 616
Unrecognized tax benefits that would Impact income tax expense and the effective tax rate |  | 1,042 |  | 1,042 |  |  |  |
Income tax expense (benefit), before any tax effect, related to accrued interest and penalties |  |  |  | (1) | (6) | 12 |  |
Accrued interest and penalties on unrecognized tax benefits |  | 37 |  | 37 | 45 |  |  |
Tax benefit resulting from favorable resolution of various uncertain tax positions |  |  | $ 39 | 7 | 113 | $ 141 |  |
Provisional net tax benefit |  | 68 |  | 1,324 |  |  |  |
Provisional tax expense resulting from the 2017 Tax Act |  | 23 |  | 457 |  |  |  |
Undistributed earnings of foreign operations |  |  |  |  |  |  | $ 5,854 |
Federal |  |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |  |
Federal, state and foreign net operating loss carryforwards |  | 111 |  | 111 |  |  |  |
State |  |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |  |
Federal, state and foreign net operating loss carryforwards |  | 2,787 |  | 2,787 |  |  |  |
Foreign Tax Authority |  |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |  |
Federal, state and foreign net operating loss carryforwards |  | 1,806 |  | 1,806 |  |  |  |
Capital loss carryforwards |  | $ 756 |  | 756 |  |  |  |
Technology Solutions |  |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |  |
Goodwill impairment charge |  |  |  | 0 | 290 |  |  |
New Accounting Pronouncement, Early Adoption, Effect |  |  |  |  |  |  |  |
Income Tax Contingency [Line Items] |  |  |  |  |  |  |  |
Tax benefit related to adoption of amended accounting guidance |  |  |  | $ 8 | $ 54 |  |  |

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