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Equity (Tables) | 6 Months Ended
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Feb. 17, 2019
Equity [Abstract] |
Stock Repurchased During Period | Stock repurchase activity during the second quarter and first half of 2019 and 2018 is summarized below:
| Shares Repurchased (000's) |  | Average Price per Share |  | Total Cost
Second quarter of 2019 | 561 |  |  | $ | 208.72 |  |  | $ | 117 |
First half of 2019 | 711 |  |  | $ | 213.08 |  |  | $ | 151 |
Second quarter of 2018 | 313 |  |  | $ | 187.70 |  |  | $ | 59 |
First half of 2018 | 1,047 |  |  | $ | 170.06 |  |  | $ | 178 |

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- Definition Schedule of Common Stock Repurchased And Average Price Paid Per Share [Table Text Block] + References No definition available. + Details
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Namespace Prefix: | cost_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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- References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration