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Share Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Millions | 1 Months Ended | 2 Months Ended | 3 Months Ended | 12 Months Ended | 168 Months Ended |
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Feb. 04, 2021 | Mar. 31, 2020 | Mar. 31, 2019 | Sep. 30, 2019 | Dec. 31, 2020 | Sep. 30, 2020 | Mar. 31, 2020 | Dec. 31, 2019 | Sep. 30, 2019 | Jun. 30, 2019 | Mar. 31, 2019 | Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2020 | Apr. 01, 2019
Share Repurchase Program [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
BOD authorized |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150,000,000
Stock repurchase program expiration date |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Mar. 31, 2022 |  |  |  |
Aggregate cost |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 3,705 | $ 5,804 | $ 8,225 | $ 40,900 |
Shares repurchased |  |  |  |  |  | 3,780,743 | 4,045,575 | [1] | 14,305,793 | [2] | 3,582,212 | 9,529,733 | [1] | 3,732,974 | 18,149,450 | [2] | 22,132,111 | 34,994,369 |  |  |
Average purchase price | [3] |  |  |  |  | $ 198.07 | $ 98.87 | [1] | $ 178.66 | [2] | $ 167.32 | $ 163.30 | [1] | $ 171.24 | $ 165.79 | [2] | $ 167.39 | $ 165.85 |  |  |
Remaining number of shares that may be repurchased under current authority |  |  |  |  |  | 111,022,970 |  |  |  |  |  |  |  |  |  |  | 111,022,970 |  |  | 111,022,970 |
Accelerated Share Repurchase Agreement [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Repurchase Program [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate cost |  |  | $ 2,000 | $ 2,500 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares repurchased |  |  | 8,786,380 | 11,795,930 | 3,172,900 |  | 4,045,575 |  | 8,786,380 |  |  | 3,172,900 |  |  | 11,795,930 |  |  |  |  |  |
Average purchase price |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 155.86 | $ 167.01 |  |  |
Subsequent Event [Member] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Share Repurchase Program [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Aggregate cost |  | $ 442 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Shares repurchased |  | 2,100,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
[1] | Includes an incremental 4,045,575 and 3,172,900 shares received upon final settlement in July 2020 and August 2019, respectively, under accelerated share repurchase programs.
[2] | Includes 8,786,380 and 11,795,930 shares repurchased in February 2020 and 2019, respectively, under accelerated share repurchase programs.
[3] | In the period of the final settlement, the average price paid under the accelerated share repurchase programs is calculated based on the total program value less the value assigned to the initial delivery of shares. The average price of the completed 2020 and 2019 accelerated share repurchase programs was $155.86 and $167.01, respectively.

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