Supplemental Information On Oil And Gas Operations (Standardized Measure Of Discounted Future Net Cash Flows Related To Interest In Proved Reserves) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Future cash inflows	$ 107,218	$ 95,288	$ 88,867
Future costs:
Development	(10,787)	(10,756)	(12,767)
Production	(43,972)	(42,372)	(40,876)
Future income tax expense	(14,047)	(11,373)	(8,534)
Future net cash flow	38,412	30,787	26,690
10% discount to reflect timing of cash flows	(17,938)	(15,046)	(13,469)
Standardized measure of discounted future net cash flows	20,474	15,741	13,221	17,844
United States [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Future cash inflows	75,847	61,983	55,297
Future costs:
Development	(7,168)	(5,448)	(6,556)
Production	(29,740)	(26,663)	(24,265)
Future income tax expense	(11,021)	(9,046)	(6,542)
Future net cash flow	27,918	20,826	17,934
10% discount to reflect timing of cash flows	(12,819)	(10,346)	(9,036)
Standardized measure of discounted future net cash flows	15,099	10,480	8,898
Canada [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Future cash inflows	31,371	33,305	33,570
Future costs:
Development	(3,619)	(5,308)	(6,211)
Production	(14,232)	(15,709)	(16,611)
Future income tax expense	(3,026)	(2,327)	(1,992)
Future net cash flow	10,494	9,961	8,756
10% discount to reflect timing of cash flows	(5,119)	(4,700)	(4,433)
Standardized measure of discounted future net cash flows	$ 5,375	$ 5,261	$ 4,323

Supplemental Information On Oil And Gas Operations (Standardized Measure Of Discounted Future Net Cash Flows Related To Interest In Proved Reserves) (Details) (USD $)
In Millions, unless otherwise specified

Dec. 31, 2014

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]

Future cash inflows

$ 107,218us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows

$ 95,288us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows

$ 88,867us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows

Future costs:

Development

(10,787)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts

(10,756)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts

(12,767)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts

Production

(43,972)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts

(42,372)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts

(40,876)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts

Future income tax expense

(14,047)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense

(11,373)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense

(8,534)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense

Future net cash flow

38,412us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows

30,787us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows

26,690us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows

10% discount to reflect timing of cash flows

(17,938)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows

(15,046)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows

(13,469)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows

Standardized measure of discounted future net cash flows

20,474us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves

15,741us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves

13,221us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves

17,844us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves

United States [Member]

Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]

Future cash inflows

75,847us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows
/ us-gaap_StatementGeographicalAxis
= country_US

61,983us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows
/ us-gaap_StatementGeographicalAxis
= country_US

55,297us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows
/ us-gaap_StatementGeographicalAxis
= country_US

Future costs:

Development

(7,168)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_US

(5,448)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_US

(6,556)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_US

Production

(29,740)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts
/ us-gaap_StatementGeographicalAxis
= country_US

(26,663)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts
/ us-gaap_StatementGeographicalAxis
= country_US

(24,265)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts
/ us-gaap_StatementGeographicalAxis
= country_US

Future income tax expense

(11,021)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense
/ us-gaap_StatementGeographicalAxis
= country_US

(9,046)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense
/ us-gaap_StatementGeographicalAxis
= country_US

(6,542)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense
/ us-gaap_StatementGeographicalAxis
= country_US

Future net cash flow

27,918us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows
/ us-gaap_StatementGeographicalAxis
= country_US

20,826us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows
/ us-gaap_StatementGeographicalAxis
= country_US

17,934us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows
/ us-gaap_StatementGeographicalAxis
= country_US

10% discount to reflect timing of cash flows

(12,819)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows
/ us-gaap_StatementGeographicalAxis
= country_US

(10,346)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows
/ us-gaap_StatementGeographicalAxis
= country_US

(9,036)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows
/ us-gaap_StatementGeographicalAxis
= country_US

Standardized measure of discounted future net cash flows

15,099us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves
/ us-gaap_StatementGeographicalAxis
= country_US

10,480us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves
/ us-gaap_StatementGeographicalAxis
= country_US

8,898us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves
/ us-gaap_StatementGeographicalAxis
= country_US

Canada [Member]

Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]

Future cash inflows

31,371us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows
/ us-gaap_StatementGeographicalAxis
= country_CA

33,305us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows
/ us-gaap_StatementGeographicalAxis
= country_CA

33,570us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows
/ us-gaap_StatementGeographicalAxis
= country_CA

Future costs:

Development

(3,619)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_CA

(5,308)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_CA

(6,211)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts
/ us-gaap_StatementGeographicalAxis
= country_CA

Production

(14,232)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts
/ us-gaap_StatementGeographicalAxis
= country_CA

(15,709)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts
/ us-gaap_StatementGeographicalAxis
= country_CA

(16,611)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts
/ us-gaap_StatementGeographicalAxis
= country_CA

Future income tax expense

(3,026)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense
/ us-gaap_StatementGeographicalAxis
= country_CA

(2,327)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense
/ us-gaap_StatementGeographicalAxis
= country_CA

(1,992)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense
/ us-gaap_StatementGeographicalAxis
= country_CA

Future net cash flow

10,494us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows
/ us-gaap_StatementGeographicalAxis
= country_CA

9,961us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows
/ us-gaap_StatementGeographicalAxis
= country_CA

8,756us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows
/ us-gaap_StatementGeographicalAxis
= country_CA

10% discount to reflect timing of cash flows

(5,119)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows
/ us-gaap_StatementGeographicalAxis
= country_CA

(4,700)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows
/ us-gaap_StatementGeographicalAxis
= country_CA

(4,433)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows
/ us-gaap_StatementGeographicalAxis
= country_CA

Standardized measure of discounted future net cash flows

$ 5,375us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves
/ us-gaap_StatementGeographicalAxis
= country_CA

$ 5,261us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves
/ us-gaap_StatementGeographicalAxis
= country_CA

$ 4,323us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves
/ us-gaap_StatementGeographicalAxis
= country_CA

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Amount of estimated future accumulated cash inflow from the sale of proved oil and gas reserves.

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Amount of estimated future accumulated cash outflow for costs to be incurred in developing proved oil and gas reserves.

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Amount of estimated future accumulated cash outflow for income tax, based on the future income less future expense derived from production and sale of proved oil and gas reserves.

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Amount, after future accumulated cash outflow for development and production costs and future income tax, of estimated future accumulated cash inflow from the sale of proved oil and gas reserves.

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Amount of estimated future accumulated cash outflow for costs to be incurred in producing proved oil and gas reserves.

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Amount of discount on future accumulated cash inflow, after deducting future accumulated cash outflow for development and production costs and future income tax, from sale of proved oil and gas reserves, using a discount rate of ten percent a year.

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Amount of discounted future accumulated cash inflow relating to proved oil and gas reserves.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 30

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62424-109447

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 35

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62500-109447

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 55

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=34713648&loc=d3e63123-109448

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 932

-SubTopic 235

-Section 50

-Paragraph 31

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=8451039&loc=d3e62455-109447

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