The employer's best estimate, as soon as it can be reasonably determined, of contributions expected to be paid to the plan in the current remaining fiscal period. Estimated contributions may be presented in the aggregate combining (1) contributions required by funding regulations or laws, (2) discretionary contributions, and (3) noncash contributions.

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- Definition

An assumption as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 87

-Paragraph 264

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph j

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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- Definition

The total amount of net periodic benefit cost for defined benefit plans for the period. Periodic benefit costs include the following components: service cost, interest cost, expected return on plan assets, gain or loss, prior service cost or credit, transition asset or obligation, and gain or loss due to settlements or curtailments).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 132R

-Paragraph 5

-Subparagraph h

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- Definition

Aggregate carrying amount, as of the balance sheet date, of noncurrent obligations not separately disclosed in the balance sheet due to materiality considerations. Noncurrent liabilities are expected to be paid after one year (or the normal operating cycle, if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 24

-Article 5

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Retirement Plan (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
Retirement Plan (Narrative) (Details) (USD $)	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Expected long-term annual rate of return on plan assets			8.00%
Estimated contributions in 2011	$ 10,000,000		$ 10,000,000
Other long-term liabilities	138,763,000		138,763,000		80,985,000
Post-retirement benefit costs	2,729,000	1,940,000	6,409,000	5,819,000
Frontier Refineries [Member] \| Other Post-Retirement Healthcare and Other Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Other long-term liabilities	45,300,000		45,300,000
Other Post-Retirement Healthcare and Other Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Post-retirement benefit costs	$ 800,000