Cash Flow Disclosures (Cash Flow Activities) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Supplemental Quarterly Information [Abstract]
Decrease (increase) in accounts receivable	$ 302,602	$ (7,251)
Decrease (increase) in inventories	(60,562)us-gaap_IncreaseDecreaseInInventories	958us-gaap_IncreaseDecreaseInInventories
Increase in prepaid expenses	(6,825)	(42,128)
Decrease in deferred income tax assets	5,040	6,845
Decrease in accounts payable and accrued liabilities	(17,281)	(4,923)
Increase in current income tax liabilities	35,833	65,172
Total	258,807	18,673
Cash income taxes paid, net of refunds	28,280us-gaap_IncomeTaxesPaidNet	101,295us-gaap_IncomeTaxesPaidNet
Interest paid, net of amounts capitalized	(64)us-gaap_InterestPaidNet	(4,303)us-gaap_InterestPaidNet
Asset retirement costs capitalized	6,380mur_NoncashAssetRetirementObligation	22,743mur_NoncashAssetRetirementObligation
Decrease in capital expenditure accrual	$ 239,572	$ 146,790

Noncash additions to property, plant and equipment for asset retirement costs capitalized.

No definition available.

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- Definition

Future cash outflow to pay for purchases of fixed assets that have occurred.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

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- Definition

The amount of cash paid during the current period to foreign, federal, state, and local authorities as taxes on income, net of any cash received during the current period as refunds for the overpayment of taxes.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586

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The increase (decrease) during the reporting period in the amounts payable to vendors for goods and services received and the amount of obligations and expenses incurred but not paid.

+ References

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)

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- Definition

The increase (decrease) during the reporting period in amount due within one year (or one business cycle) from customers for the credit sale of goods and services.

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- Definition

The increase (decrease) during the period in the amount due for taxes based on the reporting entity's earnings or attributable to the entity's income earning process (business presence) within a given jurisdiction.

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- Definition

The increase (decrease) during the reporting period in the account that represents the temporary difference that results from Income or Loss that is recognized for accounting purposes but not for tax purposes and vice versa.

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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.

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

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- Definition

The increase (decrease) during the reporting period in the amount of outstanding money paid in advance for goods or services that bring economic benefits for future periods.

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- Definition

The amount of cash paid for interest during the period net of cash paid for interest that is capitalized.

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