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Business Acquisitions and Divestitures (Details) - USD ($) |  | 3 Months Ended | 12 Months Ended |  |  |  |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 09, 2020 | Mar. 31, 2020 | Sep. 30, 2019 | Mar. 31, 2022 | Mar. 31, 2021 | Mar. 31, 2020 | Mar. 10, 2020 | Jul. 01, 2019 | Apr. 01, 2019 | Mar. 31, 2019 | Mar. 31, 2017
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Common stock, par value (in dollars per share) |  |  |  | $ 0.01 | $ 0.01 |  |  |  |  |  |
Cumulative effect adjustment |  | $ 5,309,000,000 |  | $ (1,792,000,000) | $ 175,000,000 | $ 5,309,000,000 |  |  |  | $ 8,287,000,000 |
Equity earnings and charges from investment in Change Healthcare Joint Venture |  |  |  | (43,000,000) | $ (48,000,000) | (36,000,000) |  |  |  |  |
Tax Receivable Agreement (“TRA”) |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Percentage of net cash tax savings realized or deemed realized under TRA (percent) |  |  |  |  | 85.00% |  |  |  |  |  |
Tax Receivable Agreement (“TRA”) | Change Healthcare | Other Segments [Member] |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Noncurrent liability |  |  |  | 0 | $ 0 |  |  |  |  |  |
Retained Earnings |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Cumulative effect adjustment |  | 13,022,000,000 |  | $ 9,030,000,000 | $ 8,202,000,000 | 13,022,000,000 |  |  |  | 12,409,000,000 |
Opening retained earnings adjustments: adoption of new accounting standards |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Cumulative effect adjustment |  | (13,000,000) |  |  |  | (13,000,000) |  |  |  | 11,000,000 |
Opening retained earnings adjustments: adoption of new accounting standards | Retained Earnings |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Cumulative effect adjustment |  | (13,000,000) |  |  |  | (13,000,000) |  |  | $ 69,000,000 | $ 11,000,000 |
Separation of Change Healthcare JV |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Shares distributed in split-off (in shares) | 176,000,000 |  |  |  |  |  |  |  |  |  |
Shares of common stock exchanged (in shares) | 15,400,000 |  |  |  |  |  |  |  |  |  |
Number of shares converted into per share converted (shares) |  |  |  |  |  |  | 1 |  |  |  |
Common stock, par value (in dollars per share) |  |  |  |  |  |  | $ 0.001 |  |  |  |
Change Healthcare |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Shares repurchased (in shares) | 15,400,000 |  |  |  |  |  |  |  |  |  |
Gain from sale of equity method investment | $ 414,000,000 | 414,000,000 |  |  |  |  |  |  |  |  |
Corporate Joint Venture |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest in Joint Venture (percent) |  |  |  |  |  |  |  |  |  |  | 70.00%
Gain (Loss) on Disposition of Stock in Subsidiary or Equity Method Investee |  |  | $ 246,000,000 |  |  |  |  |  |  |  |
Corporate Joint Venture | Transition Services Agreements (“TSA”) |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Total fees charged under the TSA |  |  |  |  |  | 22,000,000 |  |  |  |  |
Corporate Joint Venture | Change Healthcare |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest in Joint Venture (percent) |  |  |  |  |  |  |  | 58.50% |  |  |
Gain (Loss) on Disposition of Stock in Subsidiary or Equity Method Investee |  |  |  |  |  | 246,000,000 |  |  |  |  |
Pre-tax other-than-temporary impairment |  |  | $ 1,200,000,000 |  |  | 1,200,000,000 |  |  |  |  |
Gain from sale of equity method investment |  | $ 414,000,000 |  |  |  | (414,000,000) |  |  |  |  |
Equity earnings and charges from investment in Change Healthcare Joint Venture |  |  |  |  |  | $ 119,000,000 |  |  |  |  |
Corporate Joint Venture | Change Healthcare | Opening retained earnings adjustments: adoption of new accounting standards | ASU 2014-09 | Retained Earnings |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Cumulative effect adjustment |  |  |  |  |  |  |  |  | $ 80,000,000 |  |
Corporate Joint Venture | Change Healthcare, Inc. |  |  |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |  |  |
Ownership interest in Joint Venture (percent) |  |  |  |  |  |  |  |  |  |  | 30.00%

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