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Employee Benefit Plans (Defined Contribution Plans) (Details) - USD ($) $ in Millions | 12 Months Ended
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Dec. 27, 2017 | Dec. 28, 2016 | Dec. 30, 2015
Defined Contribution Plan Disclosure [Line Items] |  |  |
Employer contributions | $ 2.0 | $ 2.2 | $ 1.6
Defined contribution 401(k) plan [Member] |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Maximum annual contribution per employee | 25.00% |  |
Employer matching contribution | 4.00% |  | 3.00%
Non-qualified deferred compensation plan [Member] |  |  |
Defined Contribution Plan Disclosure [Line Items] |  |  |
Maximum annual contribution per employee | 50.00% |  |
Maximum incentive compensation deferral | 100.00% |  |
Employer matching contribution |  |  | 3.00%

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- Definition Defined Contribution Plan, Maximum Amount of Incentive Compensation Deferred, Percent + References No definition available. + Details
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Namespace Prefix: | denn_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of cost for defined contribution plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -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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- 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 Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
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- Definition Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan. + References No definition available. + Details
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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |