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Subsequent Events (Details) - $ / shares shares in Millions | 2 Months Ended | 12 Months Ended |
--- | --- | --- | ---
Feb. 21, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Jan. 31, 2018
Common Stock |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Shares repurchased (in shares) |  | 2.4 | 0.2 | 1.7 |
Average price (in usd per share) |  | $ 173.19 | $ 161.16 | $ 209.39 |
Subsequent Event | January 2018 Plan |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Shares repurchased (in shares) | 0.7 |  |  |  |
Average price (in usd per share) | $ 193.18 |  |  |  |
Subsequent Event | Common Stock |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Stock repurchase plan, number of remaining shares to be repurchased (in shares) |  |  |  |  | 5.0
Subsequent Event | Common Stock | January 2018 Plan |  |  |  |  |
Subsequent Event [Line Items] |  |  |  |  |
Stock repurchase program, number of shares authorized (in shares) |  |  |  |  | 3.4

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- Definition The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. + References No definition available. + Details
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- Definition Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event. + References No definition available. + Details
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- Definition Total cost of shares repurchased divided by the total number of shares repurchased. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 + Details
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- Definition Number of shares that have been repurchased during the period and are being held in treasury. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644 + Details
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- Details
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