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Employee Benefit Plans - Narrative (Details) - USD ($) $ in Millions | 12 Months Ended
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Aug. 31, 2019 | Aug. 25, 2018 | Aug. 26, 2017
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Contributions charged to expense under the plan | $ 19.7 | $ 18.1 | $ 15.0
SERP |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Amounts charged to expense related to the plan | 2.1 | 2.1 | 2.5
Accumulated benefit obligations | 27.4 | 21.7 |
UniFirst Plan |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Amounts charged to expense related to the plan | $ 0.3 | 0.3 | 0.5
Minimum annual interest rate | 3.25% |  |
Textilease Plan |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Amounts charged to expense related to the plan | $ 0.5 | 0.2 | $ 0.2
Minimum annual interest rate | 1.50% |  |
Pension Plans |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Accumulated benefit obligations | $ 5.6 | $ 7.4 |

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- Definition Defined benefit plan minimum annual interest rate. + References No definition available. + Details
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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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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
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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942 + Details
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