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Commitments and Contingencies Operating Leases (Details) (USD $) | 3 Months Ended | 9 Months Ended | 0 Months Ended
--- | --- | --- | ---
Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 | Sep. 30, 2012 | Jul. 26, 2013 Tyler Lease and Access Agreement [Member]
Related Party Transaction [Line Items] |  |  |  |  |
Related party transaction, annual lease payment |  |  |  |  | $ 100.00
Operating Leases, Rent Expense | $ 100,000 | $ 100,000 | $ 300,000 | $ 200,000 |

X
- Definition The yearly payments due under the lease entered into in with related party. + References No definition available. + Details
Name: | dk_Relatedpartytransactionannualleasepayment
Namespace Prefix: | dk_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line. + References No definition available. + Details
Name: | us-gaap_LeaseAndRentalExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration