Long-Term Debt (Details) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 25, 2013
Line of Credit Facility [Line Items]
Weighted-average interest rate (in hundredths)	2.17%	2.17%
Maturity date	Apr. 24, 2018
Interest Rate Cap [Member] \| Interest Rate Cap 2013-2014 [Member]
Line of Credit Facility [Line Items]
Derivative, notional amount	125,000,000
Interest rate cap, basis spread on variable rate (percent)	2.00%
Interest Rate Cap [Member] \| Interest Rate Cap 2014-2015 [Member]
Line of Credit Facility [Line Items]
Derivative, notional amount	150,000,000
Interest rate cap, basis spread on variable rate (percent)	2.00%
Interest Rate Swap [Member]
Line of Credit Facility [Line Items]
Average fixed interest rate on interest rate swap	3.13%
Fair value of interest rate swap	642,000
Interest Rate Swap [Member] \| Not Designated as Hedging Instrument [Member]
Line of Credit Facility [Line Items]
Derivative, notional amount	30,000,000
Interest Rate Swap [Member] \| Designated as Hedging Instrument [Member]
Line of Credit Facility [Line Items]
Derivative, notional amount	120,000,000
Secured debt [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	60,000,000
Outstanding amount under credit facility	54,800,000
Debt Instrument, Periodic Amortization, Principal, Years One and Two	5.00%
Debt Instrument, Periodic Amortization, Principal, Years Three and Four	7.50%
Debt Instrument, Periodic Amortization, Principal, Year Five	10.00%
Repayments of term loan under the credit facility	3,000,000
Basis spread on variable rate (in hundredths)	2.00%
Senior secured revolver [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	190,000,000
Outstanding amount under credit facility	85,300,000
Availability under the revolving facility	79,000,000
Accordion feature that allows increase in size of facility	240,000,000
Commitment fee for unused portion of revolving credit facility (in hundredths)	0.35%
Letter of credit [Member]
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	30,000,000
Outstanding amount under letter of credit	25,700,000

Represents the amount the accordion feature allows the entity to increase the size of the credit facility to.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Annual amortization percentage of the original principal balance of term loan debt required to be paid in year five.

+ References

No definition available.

+ Details

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Namespace Prefix:	denn_
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Balance Type:	na
Period Type:	duration

- Definition

Annual amortization percentage of the original principal balance of term loan debt required to be paid in years one and two.

+ References

No definition available.

+ Details

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Namespace Prefix:	denn_
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- Definition

Annual amortization percentage of the original principal balance of term loan debt required to be paid in years three and four.

+ References

No definition available.

+ Details

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Namespace Prefix:	denn_
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Balance Type:	na
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- Definition

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column B

+ Details

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Definition

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

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-Topic 815

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-Section 45

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-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

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-Topic 210

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-Paragraph 3

-Subparagraph (c)

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-Topic 815

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-Topic 210

-SubTopic 20

-Section 55

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+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Average fixed interest rate related to the group of interest rate derivatives.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The percentage points added to the reference rate to compute the variable rate on the interest rate derivative.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.16)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 20, 22

-Article 5

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-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.16)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(b),22(b))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19, 22

-Article 5

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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

- Definition

Weighted average interest rate of long-term debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The cash outflow for a long-term debt where the holder has highest claim on the entity's asset in case of bankruptcy or liquidation during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 15

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3291-108585

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-Publisher FASB

-Name Accounting Standards Codification

-Glossary Financing Activities

-URI http://asc.fasb.org/extlink&oid=6513228

+ Details

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Balance Type:	credit
Period Type:	duration

- Details

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- Details

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- Details

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- Details

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