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Summary of Significant Accounting Policies - Derivative Instruments (Details) | 12 Months Ended
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Dec. 25, 2024
Accounting Policies [Abstract] |
Derivative Asset, Statement Of Financial Position, Extensible Enumeration Not Disclosed Flag | Consolidated Balance Sheets
Derivative Liability, Statement Of Financial Position, Extensible Enumeration Not Disclosed Flag | Consolidated Balance Sheets

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- Definition Derivative Asset, Statement Of Financial Position, Extensible Enumeration Not Disclosed Flag + References No definition available. + Details
Name: | denn_DerivativeAssetStatementOfFinancialPositionExtensibleEnumerationNotDisclosedFlag
Namespace Prefix: | denn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Derivative Liability, Statement Of Financial Position, Extensible Enumeration Not Disclosed Flag + References No definition available. + Details
Name: | denn_DerivativeLiabilityStatementOfFinancialPositionExtensibleEnumerationNotDisclosedFlag
Namespace Prefix: | denn_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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