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Common Stock Repurchase Program (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended |  |
--- | --- | --- | --- | --- | ---
Sep. 30, 2019 | May 31, 2019 | Jan. 31, 2019 | Mar. 31, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018 | Dec. 31, 2018 | Dec. 31, 2017
Accelerated Share Repurchases [Line Items] |  |  |  |  |  |  |  |  |
Cash paid for repurchase of common stock |  |  |  |  |  | $ 248 | $ 750 |  |
Total repurchases |  |  |  |  | $ 200 | 244 | $ 750 |  |
Authorized share repurchases | $ 1,300 |  |  |  |  | $ 1,300 |  | $ 1,500 | $ 1,250
10b5-1 Plan [Member] |  |  |  |  |  |  |  |  |
Accelerated Share Repurchases [Line Items] |  |  |  |  |  |  |  |  |
Cash paid for repurchase of common stock |  |  | $ 4 |  |  |  |  |  |
Shares repurchased (in shares) |  |  |  | 0.7 |  |  |  |  |
Total repurchases |  |  |  | $ 64 |  |  |  |  |
Weighted average per share purchase price |  |  |  | $ 94.35 |  |  |  |  |
Accelerated Share Repurchase Agreement (ASR) [Member] |  |  |  |  |  |  |  |  |
Accelerated Share Repurchases [Line Items] |  |  |  |  |  |  |  |  |
Cash paid for repurchase of common stock |  | $ 180 |  |  |  |  |  |  |
Shares repurchased (in shares) | 0.3 | 1.3 |  |  |  |  |  |  |
Weighted average per share purchase price | $ 114.76 |  |  |  |  |  |  |  |
Authorized share repurchases |  | $ 180 |  |  |  |  |  |  |
Stock price (in dollars per share) |  | $ 109.59 |  |  |  |  |  |  |

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- Definition Final price paid per share for the purchase of the targeted number of shares, determined by an average market price over a fixed period of time. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 25 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6405686&loc=d3e22802-112653 + Details
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- Definition The price paid per share to immediately purchase the targeted number of shares on the date of executing the accelerated share repurchase agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 25 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6405686&loc=d3e22802-112653 + Details
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- Definition The cash outflow to reacquire common stock during the period. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 15 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3291-108585 + Details
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- Definition Amount of stock repurchase plan authorized. + References No definition available. + Details
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