General Accounting and Disclosure Matters	3 Months Ended
Mar. 31, 2018
Accounting Policies [Abstract]
General Accounting and Disclosure Matters	General Accounting and Disclosure Matters Fair Value Measurements The carrying amounts reported in the unaudited condensed consolidated balance sheets for cash and cash equivalents, accounts receivable and accounts payable approximates fair value because of the immediate or short-term maturity of these financial instruments. Marketable securities are recorded at fair value based on market quotations from actively traded liquid markets. A three-tier hierarchy has been established that classifies fair value amounts recognized in the financial statements based on the observability of inputs used to estimate such fair values. The hierarchy considers fair value amounts based on observable inputs (Levels 1 and 2) to be more reliable and predictable than those based primarily on unobservable inputs (Level 3). At each balance sheet reporting date, we categorize our financial assets and liabilities using this hierarchy. Fair value contracts consist of derivative financial instruments and are recorded as either an asset or liability measured at its fair value. Changes in fair value are recognized immediately in earnings unless the derivatives qualify for, and we elect, cash flow hedge accounting. We had no contracts designated for hedge accounting during any current reporting periods (see Note 9 for further information). Investments in Unconsolidated Affiliates As a result of the voluntary bankruptcy filing in April 2017 of one of our wholly owned subsidiaries, Adams Resources Exploration Corporation (“AREC”), and our loss of control of AREC, we deconsolidated AREC in April 2017, and we recorded our investment in this subsidiary under the cost method of accounting. At March 31, 2018, our remaining investment in AREC was $0.4 million. We expect the bankruptcy case to be dismissed during the second quarter of 2018. Income Taxes Income taxes are accounted for using the asset and liability method. Under this approach, deferred tax assets and liabilities are recognized based on anticipated future tax consequences attributable to differences between financial statement carrying amounts of these items and their respective tax basis. On December 22, 2017, the Tax Cut and Jobs Act was enacted into law resulting in a reduction in the federal corporate income tax rate from 35 percent to 21 percent for years beginning in 2018, which impacts our income tax provision or benefit. Letter of Credit Facility We maintain a Credit and Security Agreement with Wells Fargo Bank, National Association to provide up to a $60 million stand-by letter of credit facility used to support crude oil purchases within our crude oil marketing segment and for other purposes. We are currently using the letter of credit facility for a letter of credit related to our insurance program. This facility is collateralized by the eligible accounts receivable within our crude oil marketing segment and expires on August 27, 2019. The issued stand-by letters of credit are canceled as the underlying purchase obligations are satisfied by cash payment when due. The letter of credit facility places certain restrictions on Gulfmark Energy, Inc., one of our wholly owned subsidiaries. These restrictions include the maintenance of positive net earnings excluding inventory valuation changes, as defined, among other restrictions. We are currently in compliance with all such financial covenants. At March 31, 2018 and December 31, 2017, we had $0.4 million and $2.2 million, respectively, outstanding under this facility. Property and Equipment Property and equipment is recorded at cost. Expenditures for additions, improvements and other enhancements to property and equipment are capitalized, and minor replacements, maintenance and repairs that do not extend asset life or add value are charged to expense as incurred. When property and equipment assets are retired or otherwise disposed of, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in results of operations in operating costs and expenses for the respective period. Property and equipment, except for land, is depreciated using the straight-line method over the estimated average useful lives of three to twenty years. We review our long-lived assets for impairment whenever there is evidence that the carrying value of such assets may not be recoverable. Any impairment recognized is permanent and may not be restored. Property and equipment is reviewed at the lowest level of identifiable cash flows. For properties requiring impairment, the fair value is estimated based on an internal discounted cash flow model. Cash flows are developed based on estimated future production, and prices are then discounted using a market based rate of return consistent with that used by us in evaluating cash flows for other assets of a similar nature. See Note 5 for additional information regarding our property and equipment. Recent Accounting Developments In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Codification (“ASC”) 842, Leases (“ASC 842”), which requires substantially all leases (with the exception of leases with a term of one year or less) to be recorded on the balance sheet using a method referred to as the right-of-use (“ROU”) asset approach. We plan to adopt the new standard on January 1, 2019 using the modified retrospective approach. The new standard introduces two lease accounting models, which result in a lease being classified as either a “finance” or “operating” lease on the basis of whether the lessee effectively obtains control of the underlying asset during the lease term. A lease would be classified as a finance lease if it meets one of five classification criteria, four of which are generally consistent with current lease accounting guidance. By default, a lease that does not meet the criteria to be classified as a finance lease will be deemed an operating lease. Regardless of classification, the initial measurement of both lease types will result in the balance sheet recognition of a ROU asset representing a company’s right to use the underlying asset for a specified period of time and a corresponding lease liability. The lease liability will be recognized at the present value of the future lease payments, and the ROU asset will equal the lease liability adjusted for any prepaid rent, lease incentives provided by the lessor, and any indirect costs. The subsequent measurement of each type of lease varies. Leases classified as a finance lease will be accounted for using the effective interest method. Under this approach, a lessee will amortize the ROU asset (generally on a straight-line basis in a manner similar to depreciation) and the discount on the lease liability (as a component of interest expense). Leases classified as an operating lease will result in the recognition of a single lease expense amount that is recorded on a straight-line basis (or another systematic basis, if more appropriate). We have started the process of reviewing our lease agreements in light of the new guidance. Although we are in the early stages of our ASC 842 implementation project, we anticipate that this new lease guidance will cause significant changes to the way leases are recorded, presented and disclosed in our consolidated financial statements.

General Accounting and Disclosure Matters

Fair Value Measurements

The carrying amounts reported in the unaudited condensed consolidated balance sheets for cash and cash equivalents, accounts receivable and accounts payable approximates fair value because of the immediate or short-term maturity of these financial instruments. Marketable securities are recorded at fair value based on market quotations from actively traded liquid markets.

A three-tier hierarchy has been established that classifies fair value amounts recognized in the financial statements based on the observability of inputs used to estimate such fair values. The hierarchy considers fair value amounts based on observable inputs (Levels 1 and 2) to be more reliable and predictable than those based primarily on unobservable inputs (Level 3). At each balance sheet reporting date, we categorize our financial assets and liabilities using this hierarchy.

Fair value contracts consist of derivative financial instruments and are recorded as either an asset or liability measured at its fair value. Changes in fair value are recognized immediately in earnings unless the derivatives qualify for, and we elect, cash flow hedge accounting. We had no contracts designated for hedge accounting during any current reporting periods (see Note 9 for further information).

Investments in Unconsolidated Affiliates

As a result of the voluntary bankruptcy filing in April 2017 of one of our wholly owned subsidiaries, Adams Resources Exploration Corporation (“AREC”), and our loss of control of AREC, we deconsolidated AREC in April 2017, and we recorded our investment in this subsidiary under the cost method of accounting. At March 31, 2018, our remaining investment in AREC was $0.4 million. We expect the bankruptcy case to be dismissed during the second quarter of 2018.

Income Taxes

Income taxes are accounted for using the asset and liability method. Under this approach, deferred tax assets and liabilities are recognized based on anticipated future tax consequences attributable to differences between financial statement carrying amounts of these items and their respective tax basis. On December 22, 2017, the Tax Cut and Jobs Act was enacted into law resulting in a reduction in the federal corporate income tax rate from 35 percent to 21 percent for years beginning in 2018, which impacts our income tax provision or benefit.

Letter of Credit Facility

We maintain a Credit and Security Agreement with Wells Fargo Bank, National Association to provide up to a $60 million stand-by letter of credit facility used to support crude oil purchases within our crude oil marketing segment and for other purposes. We are currently using the letter of credit facility for a letter of credit related to our insurance program. This facility is collateralized by the eligible accounts receivable within our crude oil marketing segment and expires on August 27, 2019.

The issued stand-by letters of credit are canceled as the underlying purchase obligations are satisfied by cash payment when due. The letter of credit facility places certain restrictions on Gulfmark Energy, Inc., one of our wholly owned subsidiaries. These restrictions include the maintenance of positive net earnings excluding inventory valuation changes, as defined, among other restrictions. We are currently in compliance with all such financial covenants. At March 31, 2018 and December 31, 2017, we had $0.4 million and $2.2 million, respectively, outstanding under this facility.

Property and Equipment

Property and equipment is recorded at cost. Expenditures for additions, improvements and other enhancements to property and equipment are capitalized, and minor replacements, maintenance and repairs that do not extend asset life or add value are charged to expense as incurred. When property and equipment assets are retired or otherwise disposed of, the related cost and accumulated depreciation is removed from the accounts and any resulting gain or loss is included in results of operations in operating costs and expenses for the respective period. Property and equipment, except for land, is depreciated using the straight-line method over the estimated average useful lives of three to twenty years.

We review our long-lived assets for impairment whenever there is evidence that the carrying value of such assets may not be recoverable. Any impairment recognized is permanent and may not be restored. Property and equipment is reviewed at the lowest level of identifiable cash flows. For properties requiring impairment, the fair value is estimated based on an internal discounted cash flow model. Cash flows are developed based on estimated future production, and prices are then discounted using a market based rate of return consistent with that used by us in evaluating cash flows for other assets of a similar nature.

See Note 5 for additional information regarding our property and equipment.

Recent Accounting Developments

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Codification (“ASC”) 842, Leases (“ASC 842”), which requires substantially all leases (with the exception of leases with a term of one year or less) to be recorded on the balance sheet using a method referred to as the right-of-use (“ROU”) asset approach. We plan to adopt the new standard on January 1, 2019 using the modified retrospective approach.

The new standard introduces two lease accounting models, which result in a lease being classified as either a “finance” or “operating” lease on the basis of whether the lessee effectively obtains control of the underlying asset during the lease term. A lease would be classified as a finance lease if it meets one of five classification criteria, four of which are generally consistent with current lease accounting guidance. By default, a lease that does not meet the criteria to be classified as a finance lease will be deemed an operating lease. Regardless of classification, the initial measurement of both lease types will result in the balance sheet recognition of a ROU asset representing a company’s right to use the underlying asset for a specified period of time and a corresponding lease liability. The lease liability will be recognized at the present value of the future lease payments, and the ROU asset will equal the lease liability adjusted for any prepaid rent, lease incentives provided by the lessor, and any indirect costs.

The subsequent measurement of each type of lease varies. Leases classified as a finance lease will be accounted for using the effective interest method. Under this approach, a lessee will amortize the ROU asset (generally on a straight-line basis in a manner similar to depreciation) and the discount on the lease liability (as a component of interest expense). Leases classified as an operating lease will result in the recognition of a single lease expense amount that is recorded on a straight-line basis (or another systematic basis, if more appropriate).

We have started the process of reviewing our lease agreements in light of the new guidance. Although we are in the early stages of our ASC 842 implementation project, we anticipate that this new lease guidance will cause significant changes to the way leases are recorded, presented and disclosed in our consolidated financial statements.