|
Supplemental Oil and Gas Disclosures - Standardized Measure of Discounted Future Net Cash Flows (Details) (USD $)
In Millions, unless otherwise specified |
Dec. 31, 2014
|
Dec. 31, 2013
|
Dec. 31, 2012
|
Dec. 31, 2011
|
|---|---|---|---|---|
| Standardized Measure of Discounted Future Net Cash Flows | ||||
| Future cash inflows | $ 7,258.5us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows | $ 7,376.7us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows | $ 6,888.4us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesCashInflows | |
| Production | (2,224.5)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts | (2,142.8)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts | (1,858.3)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesProductionCosts | |
| Development | (922.0)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts | (1,001.4)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts | (655.4)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesDevelopmentCosts | |
| Dismantlement and abandonment | (475.4)wti_FutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureDismantlementAndAbandonmentCost | (441.6)wti_FutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureDismantlementAndAbandonmentCost | (508.0)wti_FutureNetCashFlowsRelatingToProvedOilAndGasReservesFutureDismantlementAndAbandonmentCost | |
| Income taxes | (948.4)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense | (986.9)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense | (1,002.1)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesIncomeTaxExpense | |
| Future net cash inflows before 10% discount | 2,688.2us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows | 2,804.0us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows | 2,864.6us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesNetCashFlows | |
| 10% annual discount factor | (985.4)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows | (1,129.4)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows | (1,018.2)us-gaap_FutureNetCashFlowsRelatingToProvedOilAndGasReservesTenPercentAnnualDiscountForEstimatedTimingOfCashFlows | |
| Standardized measure of discounted future net cash flows | $ 1,702.8us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves | $ 1,674.6us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves | $ 1,846.4us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves | $ 2,006.4us-gaap_StandardizedMeasureOfDiscountedFutureNetCashFlowsRelatingToProvedOilAndGasReserves |
| X | ||||||||||
|
- Details
|
| X | ||||||||||
|
- Definition
Amount of estimated future accumulated cash inflow from the sale of proved oil and gas reserves. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
Amount of estimated future accumulated cash outflow for costs to be incurred in developing proved oil and gas reserves. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
Amount of estimated future accumulated cash outflow for costs to be incurred in producing proved oil and gas reserves. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
Amount of discounted future accumulated cash inflow relating to proved oil and gas reserves. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
|
- Definition
Future net cash flows relating to proved oil and gas reserves future dismantlement and abandonment cost. No definition available.
|