Consolidated Statements Of Cash Flows - Supplemental Disclosures (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Supplemental Cash Flow Information [Abstract]
Trade accounts receivable and other accounts receivable	$ (25,639)	$ (31,107)	$ 3,664
Inventory	(47,967)	(3,510)	26,894
Energy commodity derivatives contracts, net of derivatives deposits	8,556	(692)	(606)
Accounts payable	8,954	(4,423)	4,107
Accrued payroll and benefits	10,596	(6,074)	3,466
Accrued interest payable	5,014	14,347	5,323
Accrued taxes other than income	1,177	(1,421)	3,699
Deferred revenue	15,904	20,264	10,485
Accrued product purchases	44,559	20,261	(13,016)
Current and noncurrent environmental liabilities	(4,766)	(7,398)	(4,904)
Other current and noncurrent assets and liabilities	(693)	(21,762)	9,250
Changes in components of operating assets and liabilities	$ 15,695	$ (21,515)	$ 48,362

The adjustment to exclude the noncash portion of, and include cash payments for environmental costs when calculating operating cash flows under the indirect method. The adjustment can include the increase (decrease) during an accounting period in total estimated obligations recorded for probable future loss attributable to environmental contamination issues.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

+ Details

Name:	us-gaap_EnvironmentalExpenseAndLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period in the amount due from customers for the credit sale of goods and services; includes accounts receivable and other types of receivables.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInAccountsAndOtherReceivables
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period in the aggregate amount of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInAccountsPayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period in the assets (liabilities) created through trading commodity-based derivative instruments.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInCommodityContractAssetsAndLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period, excluding the portion taken into income, in the liability reflecting revenue yet to be earned for which cash or other forms of consideration was received or recorded as a receivable.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInDeferredRevenue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period in the aggregate amount of obligations related to services received from employees, such as accrued salaries and bonuses, payroll taxes and fringe benefits.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period in interest payable, which represents the amount owed to note holders, bond holders, and other parties for interest earned on loans or credit extended to the reporting entity.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInInterestPayableNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period in the aggregate value of all inventory held by the reporting entity, associated with underlying transactions that are classified as operating activities.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInInventories
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period of all assets and liabilities used in operating activities.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInOperatingCapital
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) during the reporting period in other expenses incurred but not yet paid.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInOtherAccruedLiabilities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of increase (decrease) in operating assets after deduction of operating liabilities classified as other.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInOtherOperatingCapitalNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The increase (decrease) during the period in the amount of cash payments due to taxing authorities for non-income-related taxes.

+ References

+ Details

Name:	us-gaap_IncreaseDecreaseInPropertyAndOtherTaxesPayable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- References

No definition available.

+ Details

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