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Commitments and Contingencies Letters of Credit (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2013
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Letters of Credit [Abstract] |
Letters of Credit | $ 12.0

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- Details
Name: | dk_LettersOfCreditAbstract
Namespace Prefix: | dk_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- 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