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Stockholders' Equity - Narrative (Details) $ / shares in Units, £ in Millions, shares in Millions, € in Billions | 1 Months Ended | 2 Months Ended | 3 Months Ended | 12 Months Ended |  |  |  |  |
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Apr. 30, 2017 shares | Mar. 31, 2017 USD ($) $ / shares shares | Feb. 29, 2016 USD ($) | Jul. 31, 2015 $ / shares | Apr. 30, 2017 shares | Mar. 31, 2016 USD ($) $ / shares shares | Mar. 31, 2017 USD ($) $ / shares shares | Mar. 31, 2016 USD ($) $ / shares shares | Mar. 31, 2015 USD ($) $ / shares shares | Mar. 31, 2017 EUR (€) vote | Mar. 31, 2017 USD ($) vote | Mar. 31, 2017 GBP (£) vote | Oct. 31, 2016 USD ($) | Oct. 31, 2015 USD ($) | May 31, 2015 USD ($) | Mar. 31, 2014 USD ($)
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of votes | vote |  |  |  |  |  |  |  |  |  | 1 | 1 | 1 |  |  |  |
Cash dividends declared per common share (in dollars per share) | $ / shares |  |  |  |  |  |  | $ 1.12 | $ 1.08 | $ 0.96 |  |  |  |  |  |  |
Shares repurchase plans authorized |  |  |  |  |  |  |  |  |  |  |  |  | $ 4,000,000,000.0 | $ 2,000,000,000 | $ 500,000,000 |
Shares bought | shares |  |  |  |  |  |  | 15.5 | 8.7 | 1.5 |  |  |  |  |  |  |
Shares repurchased |  |  |  |  |  |  | $ 2,250,000,000 | $ 1,504,000,000 | $ 340,000,000 |  |  |  |  |  |  |
Average price paid per share (in dollars per share) | $ / shares |  |  |  |  |  |  | $ 141.16 | $ 173.64 | $ 226.55 |  |  |  |  |  |  |
Total authorization outstanding for repurchases of common stock |  |  |  |  |  | $ 996,000,000 |  | $ 996,000,000 | $ 0 |  | $ 2,746,000,000 |  |  |  |  | $ 340,000,000
Repurchase of common stock |  |  |  |  |  |  | $ 2,250,000,000 | $ 1,504,000,000 | 340,000,000 |  |  |  |  |  |  |
Treasury stock retired (in shares) | shares |  |  |  |  |  |  |  | 115.5 |  |  |  |  |  |  |  |
Other comprehensive income (loss) before reclassifications |  |  |  |  |  |  | (688,000,000) | $ 142,000,000 |  |  |  |  |  |  |  |
Net foreign currency translation gains (losses) |  |  |  |  |  |  | (659,000,000) | 172,000,000 | $ (1,989,000,000) |  |  |  |  |  |  |
Losses from net investment hedges |  |  |  |  |  |  | $ 13,000,000 |  |  |  |  |  |  |  |  |
Total debt outstanding |  |  |  |  |  | $ 8,107,000,000 |  | $ 8,107,000,000 |  |  | $ 8,362,000,000 |  |  |  |  |
Treasury Stock |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase of common stock (in shares) | shares |  |  |  |  |  |  | 16.0 | 9.0 | 2.0 |  |  |  |  |  |  |
Repurchase of common stock |  |  |  |  |  |  | $ 2,200,000,000 | $ 1,504,000,000 | $ 340,000,000 |  |  |  |  |  |  |
Retirement of common stock |  |  |  |  |  |  |  | 7,800,000,000 |  |  |  |  |  |  |  |
Retained Earnings |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retirement of common stock |  |  |  |  |  |  |  | 6,400,000,000 |  |  |  |  |  |  |  |
Additional Paid-in Capital |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Repurchase of common stock (in shares) | shares |  |  |  |  |  |  | 50.0 |  |  |  |  |  |  |  |  |
Retirement of common stock |  |  |  |  |  |  |  | 1,500,000,000 |  |  |  |  |  |  |  |
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other comprehensive income (loss) before reclassifications |  |  |  |  |  |  | $ (644,000,000) | 113,000,000 | (1,845,000,000) |  |  |  |  |  |  |
Net foreign currency translation gains (losses) |  |  |  |  |  |  | (624,000,000) | 113,000,000 | $ (1,855,000,000) |  |  |  |  |  |  |
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Net foreign currency translation gains (losses) |  |  |  |  |  |  | (74,000,000) | 16,000,000 |  |  |  |  |  |  |  |
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Including Portion Attributable to Noncontrolling Interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Other comprehensive income (loss) before reclassifications |  |  |  |  |  |  | $ (5,000,000) | $ 4,000,000 |  |  |  |  |  |  |  |
Open Market Transactions |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares bought | shares |  |  |  |  |  |  |  | 4.5 |  |  |  |  |  |  |  |
Shares repurchased |  |  |  |  |  |  |  | $ 854,000,000 |  |  |  |  |  |  |  |
Average price paid per share (in dollars per share) | $ / shares |  |  |  |  |  |  | $ 140.96 | $ 192.27 |  |  |  |  |  |  |  |
Repurchase of common stock (in shares) | shares |  |  |  |  |  |  | 14.1 |  |  |  |  |  |  |  |  |
Repurchase of common stock |  |  |  |  |  |  | $ 2,000,000,000 |  |  |  |  |  |  |  |  |
Accelerated Share Repurchase |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares bought | shares |  | 1.4 |  |  |  | 4.2 |  |  |  |  |  |  |  |  |  |
Shares repurchased |  | $ 250,000,000 | $ 650,000,000 |  |  |  |  |  |  |  |  |  |  |  |  |
Average price paid per share (in dollars per share) | $ / shares |  | $ 143.19 |  |  |  | $ 154.04 |  |  |  |  |  |  |  |  |  |
Minimum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash dividends declared per common share (in dollars per share) | $ / shares |  |  |  | $ 0.24 |  |  |  |  |  |  |  |  |  |  |  |
Maximum |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Cash dividends declared per common share (in dollars per share) | $ / shares |  |  |  | $ 0.28 |  |  |  |  |  |  |  |  |  |  |  |
Notes | Euro Denominated Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt outstanding | € |  |  |  |  |  |  |  |  |  | € 1.2 |  |  |  |  |  |
Notes | British Pound Sterling Denominated Notes |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Total debt outstanding | £ |  |  |  |  |  |  |  |  |  |  |  | £ 450 |  |  |  |
Subsequent Event | Accelerated Share Repurchase |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Dividends Payable [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares bought | shares | 0.3 |  |  |  | 1.7 |  |  |  |  |  |  |  |  |  |  |

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