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Quarterly Financial Information (Unaudited) - Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2016 | Mar. 31, 2015 | Mar. 31, 2014
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pretax charges related to last-in-first-out method of accounting for inventories |  |  |  |  |  |  |  |  | $ 244 | $ 337 | $ 311
Pre-tax charge | $ 229 |  |  |  |  |  |  |  | 229 |  |
Brazil Distribution Business |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Impairment charges, net of tax |  |  |  |  | $ 235 |  |  |  |  |  |
Controlled Substance Investigation |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Claims and litigation charges, after tax |  |  |  |  | 150 |  |  |  |  | $ 150 |
Cost of Sales |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pre-tax charge | 26 |  |  |  |  |  |  |  |  |  |
Operating Expenses |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pre-tax charge | 203 |  |  |  |  |  |  |  |  |  |
Operating Segments | Distribution Solutions |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pretax charges related to last-in-first-out method of accounting for inventories | 29 | $ 33 | $ 91 | $ 91 | $ 50 | $ 95 | $ 94 | $ 98 |  |  |
Net cash proceeds |  | $ 17 |  | 59 |  |  |  |  | 76 |  |
Pre-tax charge | 161 |  |  |  |  |  |  |  | 161 |  |
Operating Segments | Distribution Solutions | ZEE Medical Business |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gain from sale of business, after tax |  |  | $ 29 |  |  |  |  |  |  |  |
Operating Segments | Distribution Solutions | Cost of Sales |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pre-tax charge | 5 |  |  |  |  |  |  |  |  |  |
Operating Segments | Distribution Solutions | Operating Expenses |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pre-tax charge | 156 |  |  |  |  |  |  |  |  |  |
Operating Segments | Technology Solutions |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pre-tax charge | 51 |  |  |  |  |  |  |  | $ 51 |  |
Operating Segments | Technology Solutions | Nurse Triage |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Gain from sale of business, after tax |  |  |  | $ 38 |  |  |  |  |  |  |
Operating Segments | Technology Solutions | Cost of Sales |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pre-tax charge | 21 |  |  |  |  |  |  |  |  |  |
Operating Segments | Technology Solutions | Operating Expenses |  |  |  |  |  |  |  |  |  |  |
Quarterly Financial Information [Line Items] |  |  |  |  |  |  |  |  |  |  |
Pre-tax charge | $ 30 |  |  |  |  |  |  |  |  |  |

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