Defined Contribution Plan, Maximum Amount of Incentive Compensation Deferred, Percent

No definition available.

Name:	denn_DefinedContributionPlanMaximumAmountOfIncentiveCompensationDeferredPercent
Namespace Prefix:	denn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- 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

Name:	us-gaap_DefinedContributionPlanCostRecognized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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_DefinedContributionPlanDisclosureLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_PlanNameAxis=denn_Definedcontribution401kplanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=denn_NonqualifieddeferredcompensationplanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Employee Benefit Plans (Defined Contribution Plans) (Details) - USD ($) $ in Millions	12 Months Ended
	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%