Introduction and Basis of Presentation (Details)	3 Months Ended	6 Months Ended
Jun. 27, 2012	Jun. 29, 2011	Jun. 27, 2012	Jun. 29, 2011
Entity and franchisee unit activity [Abstract]
Units, end of period	1,684	1,677	1,684	1,677
Franchised/licensed restaurants [Member]
Franchisor Disclosure [Line Items]
Percentage of restaurants operated (in hundredths)	89.00%		89.00%
Entity and franchisee unit activity [Abstract]
Units, beginning of period	1,483	1,439	1,479	1,426
Units opened	9	17	15	30
Units relocated	0	1	0	1
Units purchased from Company	17	1	23	10
Units closed	(2)	(6)	(10)	(15)
Units, end of period	1,507	1,452	1,507	1,452
Entity owned restaurants [Member]
Franchisor Disclosure [Line Items]
Percentage of restaurants operated (in hundredths)	11.00%		11.00%
Entity and franchisee unit activity [Abstract]
Units, beginning of period	197	226	206	232
Units opened	0	1	0	6
Units sold to franchisees	(17)	(1)	(23)	(10)
Units closed	(3)	(1)	(6)	(3)
Units, end of period	177	225	177	225

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

Represents ownership percentage of restaurants operated by the entity or franchisees.

No definition available.

Name:	denn_PercentageOfRestaurantsOperated
Namespace Prefix:	denn_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

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 relocated during the period.

No definition available.

Represents number of units sold to franchisees during the period.

No definition available.

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

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