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Shareholders' Equity (Details) - USD ($) | 3 Months Ended | 72 Months Ended |  |  |
--- | --- | --- | --- | --- | ---
Mar. 31, 2018 | Mar. 31, 2017 | Mar. 31, 2018 | Feb. 28, 2017 | Nov. 30, 2014 | Apr. 30, 2012
Common Stock Programs |  |  |  |  |  |
Shares purchased (in shares) |  |  | 112,100,000 |  |  |
Total cost of shares purchased | $ 553,000,000 | $ 126,000,000 | $ 10,100,000,000 |  |  |
Treasury stock acquired, additional transaction costs | $ 2,800,000 | $ 600,000 |  |  |  |
Weighted average shares outstanding |  |  |  |  |  |
Shares for basic earnings per share (in shares) | 248,500,000 | 264,800,000 |  |  |  |
Dilutive effect of potentially issuable shares (in shares) | 1,700,000 | 2,200,000 |  |  |  |
Shares for diluted earnings per share (in shares) | 250,200,000 | 267,000,000 |  |  |  |
Number of shares excluded from the calculation of diluted earnings per share (in shares) | 100,000 | 0 |  |  |  |
Share Repurchase Program of 2014 |  |  |  |  |  |
Common Stock Programs |  |  |  |  |  |
Share repurchase authorization limit (up to) | $ 15,000,000,000.0 |  | 15,000,000,000.0 | $ 5,000,000,000.0 | $ 5,000,000,000.0 |
Share repurchase, remaining authorization limit (in shares) | $ 4,900,000,000 |  | $ 4,900,000,000 |  |  |
2012 - Share Repurchase Program |  |  |  |  |  |
Common Stock Programs |  |  |  |  |  |
Share repurchase authorization limit (up to) |  |  |  |  |  | $ 5,000,000,000.0
Shares purchased (in shares) | 3,900,000 | 1,100,000 |  |  |  |
Average price per share of stock repurchased (in dollars per share) | $ 140.94 | $ 114.46 |  |  |  |
Total cost of shares purchased | $ 550,000,000 | $ 125,000,000 |  |  |  |

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