Introduction and Basis of Presentation (Details)	3 Months Ended	6 Months Ended
Jun. 26, 2013 restaurant	Jun. 27, 2012 restaurant	Jun. 26, 2013 restaurant	Jun. 27, 2012 restaurant
Entity and franchisee unit activity [Abstract]
Units, end of period	1,690	1,684	1,690	1,684
Company restaurants [Member]
Entity and franchisee unit activity [Abstract]
Units, beginning of period	164	197	164	206
Units opened	0	0	0	0
Units acquired from franchisees	1	0	1	0
Units sold to franchisees	0	(17)	0	(23)
Units closed	0	(3)	0	(6)
Units, end of period	165	177	165	177
Franchised and licensed restaurants [Member]
Entity and franchisee unit activity [Abstract]
Units, beginning of period	1,525	1,483	1,524	1,479
Units opened	11	9	18	15
Units purchased from Company	0	17	0	23
Units acquired by Company	(1)	0	(1)	0
Units closed	(10)	(2)	(16)	(10)
Units, end of period	1,525	1,507	1,525	1,507

Name:	denn_EntityAndFranchiseeUnitActivityAbstract
Namespace Prefix:	denn_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Represents number of units acquired by Company during the period.

No definition available.

Name:	denn_UnitsAcquiredByCompany
Namespace Prefix:	denn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents number of units acquired from franchisees during the period.

No definition available.

Name:	denn_UnitsAcquiredFromFranchisees
Namespace Prefix:	denn_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

Represents number of units closed by an entity and franchisee during the period.

No definition available.

Represents number of units opened by an entity and franchisee during the period.

No definition available.

Represents number of units franchisees purchased from the entity during the period.

No definition available.

Represents number of units sold to franchisees during the period.

No definition available.

Represents the number of restaurants.

No definition available.

Name:	us-gaap_NumberOfRestaurants
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant