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v3.10.0.1

Segment Reporting Information by Item Category (Details) | 12 Months Ended
--- | ---
Sep. 02, 2018 | Sep. 03, 2017 | Aug. 28, 2016
Food and Sundries [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Percentage of net sales | 41.00% | 41.00% | 43.00%
Hardlines |  |  |
Revenue from External Customer [Line Items] |  |  |
Percentage of net sales | 16.00% | 16.00% | 16.00%
Fresh Foods |  |  |
Revenue from External Customer [Line Items] |  |  |
Percentage of net sales | 14.00% | 14.00% | 14.00%
Softlines |  |  |
Revenue from External Customer [Line Items] |  |  |
Percentage of net sales | 11.00% | 12.00% | 12.00%
Ancillary |  |  |
Revenue from External Customer [Line Items] |  |  |
Percentage of net sales | 18.00% | 17.00% | 15.00%

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- Definition Percentage of net sales by major item category. + References No definition available. + Details
Name: | cost_MajorItemCategoryasPercentageofNetSales
Namespace Prefix: | cost_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_EntityWideInformationRevenueFromExternalCustomerLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Details
Name: | srt_ProductOrServiceAxis=cost_FoodandSundriesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_ProductOrServiceAxis=cost_HardlinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_ProductOrServiceAxis=cost_FreshFoodMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_ProductOrServiceAxis=cost_SoftlinesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | srt_ProductOrServiceAxis=cost_OtherMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |