Long-Term Obligations and Notes Payable - DKL Notes (Details) - Senior notes - DKL Notes - USD ($)		6 Months Ended
May 23, 2017	Jun. 30, 2018
Debt Instrument [Line Items]
Face amount of debt	$ 250,000,000.0	$ 250,000,000
Stated interest rate (as percent)	6.75%
Redemption price, percentage (as percent)		101.00%
Anytime prior to May 15, 2020
Debt Instrument [Line Items]
Redemption price, percentage of principal amount redeemed (as percent)	35.00%
Redemption price, percentage (as percent)	106.75%
Twelve-month period beginning May 15, 2020
Debt Instrument [Line Items]
Redemption price, percentage (as percent)	105.063%
Twelve-month period beginning May 15, 2021
Debt Instrument [Line Items]
Redemption price, percentage (as percent)	103.375%
Twelve-month period beginning May 15, 2022
Debt Instrument [Line Items]
Redemption price, percentage (as percent)	101.688%
Twelve-month period beginning May 15, 2023 and thereafter
Debt Instrument [Line Items]
Redemption price, percentage (as percent)	100.00%

Face (par) amount of debt instrument at time of issuance.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=114775744&loc=d3e28551-108399

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
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Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
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Percentage of principal amount of debt redeemed.

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